The race for the 2024 Republican White House nomination is heating up.
Several big-name and dark-horse contenders have joined an increasingly crowded field in recent weeks.
All are seeking to unseat the current front-runner, former President Donald Trump, who continues to dominate in national opinion polls.
The eventual winner will challenge the presumptive Democratic nominee, President Joe Biden, in the general election of November next year.
Mike Pence officially launched his campaign with a speech on 7 June, putting him on a collision course with his former boss.
The speech offered his most forceful repudiation of Donald Trump to date, accusing the ex-president of being unfaithful to the US constitution and of abandoning conservative values.
It was a far cry from his role as a loyal deputy to Mr Trump as his vice-president for four years - until 2021's Capitol riot splintered their relationship.
The son of a Korean War veteran, Mr Pence began his career in conservative politics as a talk radio host.
He was elected to the House in 2000 and served until 2013, describing himself as a "principled conservative" and aligning with the Tea Party movement.
He also served as governor of Indiana from 2013-17. In that role, he passed the largest tax cut in state history, and signed bills to restrict abortion and protect religious freedom.
Mr Pence, 64, is a born-again evangelical Christian and his addition to the 2016 presidential ticket is credited with helping mobilise the crucial voting bloc on behalf of Mr Trump.
Calm and soft-spoken, he was seen as an effective surrogate to the bombastic president. But Mr Trump turned on him for lacking "courage" after he refused to help overturn the 2020 election results.
Pro-Trump rioters stormed the US Capitol in January 2021 and were heard chanting "Hang Mike Pence!". At one point, they were reportedly within 40ft (12m) of the vice-president.
The former New Jersey governor announced his candidacy on 6 June at a town hall event in New Hampshire - the state that hosts the second contest in the Republican primary race.
After his own 2016 presidential bid failed, Chris Christie allied himself with Mr Trump, leading the incoming president's transition team and preparing him for debates against Mr Biden in 2020.
But he has become a vociferous critic of Mr Trump since the US Capitol riots.
The sharp-tongued Mr Christie, 60, previewed an attack line on Mr Trump at a New Hampshire town hall in April, saying: "Donald Trump is a TV star, nothing more, nothing less. Let me suggest to you that in putting him back in the White House, the re-runs will be worse than the original show."
Mr Christie served two terms as New Jersey governor from 2010-18. Massively popular in his first term, his second was overshadowed by a political scandal involving bridge lane closures - part of an alleged political vendetta against a Democratic mayor.
Before being elected as governor, Mr Christie served as New Jersey's top prosecutor under President George W Bush from 2002-08, and famously sent Charles Kushner - the father of Mr Trump's son-in-law Jared - to prison.
Florida Governor Ron DeSantis has worked hard to emulate Mr Trump, and is often viewed as the candidate most capable of defeating him in a head-to-head race.
Boosted to the governorship by Mr Trump's endorsement in 2018, he romped to re-election in last year's midterms by more than 1.5 million votes, the largest margin in the state in more than four decades. Under his tenure, Republican voters outnumber Democrats in the state for the first time.
At 44 years old, the Harvard and Yale-educated lawyer is still a relative newcomer in US politics.
He once served in the US Navy, including a tour in Iraq. He was also a little-known member of the House of Representatives from 2013 to 2018.
But Mr DeSantis has seen his star rise considerably since he became governor, a role in which he has positioned himself as an enthusiastic culture warrior.
He has backed legislation to defund diversity and inclusion programmes, ban teaching on gender identity in public schools, ban drag shows and gender-affirming care for minors, restrict abortions and loosen gun laws. He is also mired in an escalating legal battle with Walt Disney World.
The governor has touted his record as a "blueprint" for conservative leadership, and supporters have touted him as a drama-free alternative to re-nominating the former president.
Mr Trump has responded by attacking him almost daily on social media.
Though Mr DeSantis enjoyed a considerable lead over most of his Republican rivals in earlier polling, a September poll from the University of New Hampshire suggested his popularity had taken a hit.
It indicates he is currently placed far behind Mr Trump and nearly tied with Vivek Ramaswamy, Nikki Haley and Chris Christie.
Senator Tim Scott has a decades-long career in South Carolina politics and entered the race in May with nearly $22m (£18m) - more than his rivals - in cash on hand.
The only black man to ever serve in both chambers of Congress, the 57-year-old has represented his home state in the Senate since 2013.
Mr Scott is the grandson of a cotton field worker and the son of a single mother, and he has often spoken of how his family rose "from cotton to Congress" in a lifetime.
He launched his 2024 bid vowing to turn around "a nation in retreat" and revive America's "culture of greatness".
Well-liked among his colleagues, he quickly earned endorsements from two fellow senators, including John Thune, the chamber's second highest-ranking Republican.
But he's not the only South Carolina Republican to throw their hat in the ring.
Nikki Haley announced her bid for the presidency in mid-February, becoming the first major Republican candidate to commit to taking on Mr Trump.
Once considered one of the Republican Party's brightest young prospects, Ms Haley, 51, has seen her profile diminish in recent years.
Born in South Carolina to Punjabi Sikh immigrants, Ms Haley became the youngest governor in the country in 2009.
She earned national attention in 2015 after calling for the removal of the Confederate flag from the South Carolina Capitol.
Despite saying she was "not a fan" of Mr Trump in 2016, she later accepted his nomination to be the US ambassador to the United Nations, a tenure marked by her dramatic exit from a UN Security Council meeting as a Palestinian envoy was speaking.
Her campaign, which includes a call for mandatory mental competency tests for politicians over 75 years old, stresses the need for "a new generation" of US leaders.
Ms Haley has seen her poll numbers rise since the first Republican debate in August, and they indicate she now ranks second or third with voters in the first three nominating states of Iowa, New Hampshire and South Carolina.
Vivek Ramaswamy, 37, launched his dark-horse White House bid during a late February appearance on the Fox News channel.
An Indian-American biotech entrepreneur with no previous political experience, he was a regular fixture on Fox host Tucker Carlson's daily programme, formerly the most-watched cable news show in the US.
The Harvard and Yale graduate argues the country is in the midst of a national identity crisis driven by a decline in faith, patriotism and meritocracy.
He ran a pharmaceutical company from 2014 to 2021, then co-founded Strive Asset Management, which shirks the "divisive" environmental, social and corporate governance (ESG) framework and offers itself as an alternative to large firms like Blackrock. He is also the author of Woke, Inc.: Inside Corporate America's Social Justice Scam.
Following Mr Trump's federal indictment over his alleged mishandling of classified documents, Mr Ramaswamy vowed that, if elected president, he would pardon Mr Trump of any crimes and criticised the rest of the field for not following his lead.
Like Ms Haley, Mr Ramaswamy has enjoyed more favourable poll numbers since the first Republican debate, during which the political newcomer captured the spotlight.
He drew also controversy that same week over remarks about the 11 September attacks in an interview with the Atlantic.
"I think it is legitimate to say 'How many police, how many federal agents were on the planes that hit the twin towers?'" Mr Ramaswamy said in the interview.
After he said he had been misquoted by the magazine, the Atlantic released audio from the interview showing it was an accurate quote.
Former two-term Arkansas Governor Asa Hutchinson announced his run for president during an April interview with ABC News just days after Mr Trump was indicted on criminal charges in New York.
Mr Hutchinson, 72, has said Mr Trump's legal problems are "a sideshow and distraction" that should prompt him to withdraw from the race.
The former attorney and businessman was the youngest federal prosecutor in the nation under the Ronald Reagan administration.
He also served two terms in the US House of Representatives, including as a prosecutor in Bill Clinton's impeachment trial, and was George W Bush's Drug Enforcement Administration (DEA) chief.
Presenting himself as a "non-Trump" candidate with experience and a record of leadership across multiple roles, he has vowed to lean into "common sense, consistent conservatism".
The former software executive and current North Dakota governor confirmed a run for the White House on 7 June saying: "If you want more small-town common sense in Washington and our big cities, we'll make that happen."
The New York Times assessed his candidacy: "As the leader of his deep-red state, Mr Burgum has overseen a period of significant economic expansion, but he has also assented to staunchly conservative social policies, even as he has downplayed his role in them."
Former Texas congressman Will Hurd announced he was joining the race in a June appearance on CBS News.
A former undercover CIA officer and cybersecurity executive, Mr Hurd won thrice in a majority Hispanic congressional district that sits on the US-Mexico border. But his centrist positions, particularly on immigration, put him at increasing odds with his party through the Trump years. The 45-year-old left Congress in 2021.
He has said his party cannot afford to nominate "a lawless, selfish, failed politician like Donald Trump" and must avoid a "rematch from hell" between Mr Trump and Mr Biden.
The conservative talk radio host launched an unsuccessful campaign for California governor in 2021, pledging to repeal mask and vaccine mandates.
A lawyer who grew up in Los Angeles' South Central neighbourhood, Mr Elder, 71, has slammed Democrats' "woke" agenda and the idea of systemic racism.
He announced his long-shot 2024 presidential bid by tweeting: "America is in decline, but this decline is not inevitable."
Perry Johnson, a 75-year-old businessman who tried to run for Michigan governor last year but was disqualified, joined the presidential race in March.
He is touting a plan to reignite the economy by shaving 2% in federal spending every year.
Miami's 45-year-old Cuban-born mayor, Francis Suarez, was the only Hispanic candidate in the race.
Mr Suarez launched his bid one day after Mr Trump, who he did not vote for in 2016 or 2020, appeared in his city to face federal charges related to his handling of classified documents. Trump supporters were seen verbally berating the mayor.
He was the first to drop out of the race, on 29 August, after failing to make the stage for the first Republican debate.
A business executive from Texas, Ryan Binkley is also a Christian pastor.
He has said he "heard calls from the Lord about what's needed" and will prioritise "solutions for the country".
Others who could run
Glenn Youngkin: The Virginia governor, who scored an upset victory in 2021 in a state that has trended Democratic in recent years, is reportedly reconsidering a run after previously saying he was not.
Liz Cheney: The daughter of former vice-president Dick Cheney was once a rising star in the party but lost her seat in the House of Representatives in 2021 over her fierce opposition to Mr Trump.
Greg Abbott: The Texas governor has routinely waded into national debates on immigration, abortion and gun rights.
Who is not running?
Mike Pompeo: The former secretary of state to Mr Trump toured early primary states but announced he would not run in April.
Chris Sununu: The moderate Republican, who has been a popular governor for the state of New Hampshire since 2017, said he will not seek his party's nomination.
Larry Hogan: The moderate former governor of Democrat-friendly Maryland said he did not want to be part of a crowded field that helps elect Mr Trump again.
Ted Cruz: The Texas senator placed second in the Republican primary for the 2016 presidential election behind Mr Trump but has said he will run for re-election to the Senate in 2024.
Rick Scott: The Florida senator has frequently exchanged vitriol with President Biden but says he too will run for re-election to the Senate.