Nikki Haley's announcement this week that she is running for the Republican presidential nomination in 2024 could touch off a stampede of rivals keen to join the pack chasing clear frontrunner Donald Trump.
The former US ambassador to the United Nations is likely to be followed into the race by Florida Governor Ron DeSantis, Trump's vice president Mike Pence and one-time secretary of state Mike Pompeo.
But it could be a much more crowded field if several more obscure candidates currently weighing their political futures jump in before the Republican convention in 17 months.
Here are some of the potential rivals Trump and Haley could face, none of whom has officially yet entered the race:
Ron DeSantis
At 44, the governor of Florida is a rising star of the right. In 2018, the little known DeSantis won Trump's endorsement and went on to capture the Sunshine State's top job.
While sharing Trump's political ideas, DeSantis has since cut a more calculated path and is less prone to Trump's outbursts.
He kept Florida open during the pandemic and orchestrated a series of headline-grabbing conservative actions, such as restricting discussion of gender identity in public schools and flying migrants to an island in Massachusetts.
"I have only begun to fight," he said in his midterm reelection victory speech last November.
DeSantis, who is Catholic, played varsity baseball at Yale, later joining the US Navy as a lawyer. He is married with three children, and espouses traditional family values held dear by many Republicans.
Polls still give a comfortable edge to Trump, but the gap has been narrowing over the past year and stands at around 17 points in the RealClearPolitics average.
Mike Pence
After years of unswerving loyalty to Donald Trump, his former vice president changed his tune after the mob assault on the US Capitol on January 6, 2021.
Pence called the president's actions that day "reckless" and said they "endangered me and my family."
Trump had demanded Pence, a former governor of Indiana, derail congressional certification of Joe Biden's electoral victory.
Pence refused, gaining the enmity of Trump's diehard followers, and he is currently winning only about seven percent of voter intentions, according to polls.
The 63-year-old evangelical Christian received unwelcome headlines in recent days over an FBI search of his home -- part of a wider Washington scandal over mishandled classified documents -- and a subpoena to testify before a federal probe into the Capitol riot, which he is resisting.
Mike Pompeo
Haley usually follows DeSantis and Pence in the polling, placing her just above 59-year-old former soldier, CIA director and secretary of state Pompeo.
Seen as brusque in public and curt with the media, Pompeo vowed to give the State Department back its "swagger" after being appointed by Trump take over from the hapless Rex Tillerson.
The evangelical Christian managed to stay consistently in Trump's good graces, loyally defending his boss on camera and to foreign allies.
Despite his elite education at West Point and Harvard Law, Pompeo emerged from obscurity as a businessman in Kansas when he was elected to Congress in the right-wing Tea Party wave of 2010.
During a tour for his new book he said he'd decide on a presidential bid in the coming months. But he has been traveling to early-voting states for more than a year and is expected to run.
Scott, Youngkin and others
South Carolina Senator Tim Scott, 57, openly dreams of being the first black Republican president. After his re-election in November -- with a 26-point lead over his rival -- he spoke of his grandfather who voted for Barack Obama.
"I wish he had lived long enough to see perhaps another man of color elected president... But this time let it be a Republican!"
Scott is the only Black Republican in the Senate and seen as a rising star in the party, although he has been stuck around one or two percent in polling for the primary contest.
Glenn Youngkin, a 55-year-old businessman, wrested the Virginia governorship from Democrats in 2021 and has employed classic right-wing policies such as lower taxes, and additional police funding, with headline-grabbing measures against transgender people and anti-racism programs in schools.
Youngkin was closely involved in the midterm campaign, and several Republican Party donors are reportedly ready to support him if he seeks the nomination.
Other sitting or former governors -- Larry Hogan of Maryland, Chris Christie of New Jersey and Chris Sununu of New Hampshire -- are always in the conversation, but are seen as Trump critics and may struggle to win over his support base.