(CNN) — Nikki Haley, the former South Carolina governor and United States ambassador to the United Nations, launched her bid for the 2024 Republican presidential nomination Tuesday.

But the primary is still in its early stages, and it could take months before the field fully rounds into form and candidates make more than occasional visits to states like Iowa, New Hampshire and South Carolina that will kick off the GOP’s nominating process.

Haley could stand alone for weeks or even months as the party’s only official rival to former President Donald Trump.

Here’s a look at who’s in and who is considering a 2024 run for the Republican nomination:

Donald Trump: The former president officially launched his campaign in November, days after the midterm elections. And he never really stopped running after 2020, continuing to hold campaign-style rallies with supporters.

Nikki Haley: Haley launched her presidential campaign Tuesday. It was a shift from her previous insistence she would not run against Trump. “It’s time for a new generation of leadership to rediscover fiscal responsibility, secure our border and strengthen our country, our pride and our purpose,” she said in a video announcing her bid.

Ron DeSantis: The Florida governor emerged as the top alternative to Trump in many conservatives’ eyes after his dominant reelection victory. A DeSantis announcement is likely months away, with Florida currently in the middle of its legislative session. But his memoir, accompanied by a media blitz, will drop at the end of February, and top advisers are building a political infrastructure.

Mike Pence: The former vice president’s split with Trump over the events of January 6, 2021, kicked off a consistent return to political travel. He has made clear that he believes the GOP will move on from Trump. “I think we’re going to have new leadership in this party and in this country,” Pence told CBS in January.

Tim Scott: The South Carolina senator would make a second Palmetto State Republican in the 2024 field if, as expected, he enters the race in the near future. Scott is building a political infrastructure, including hiring for a super PAC, and is set to visit Iowa for an event his team billed as focused on “faith in America.”

Ted Cruz: The Texas senator and 2016 GOP contender has not ruled out another presidential bid. But he is also seeking reelection in 2024. “I think there will be plenty of time to discuss the 2024 presidential race. I’m running for reelection to the Senate,” he told the CBS affiliate in Dallas in February.

Glenn Youngkin: The Virginia governor’s 2021 victory offered Republicans a new playbook focused on parental power in education. His political travel, including stops for a series of Republican gubernatorial candidates last year, makes clear Youngkin has ambitions beyond Virginia. He faced a setback to his push for a 15-week abortion ban when Democrats won a state senate special election earlier this year, expanding their narrow majority.

Chris Sununu: The New Hampshire governor’s timeline isn’t clear, but he recently established a political action committee that borrowed his state’s motto: “Live Free or Die.” He has positioned himself as a strong Trump opponent and alternative within the GOP. He would also start with the advantage of being universally known in an early-voting state. “I think America as a whole is looking for results-driven leadership that calls the balls and strikes like they see them and is super transparent,” Sununu told Axios this week.

Kristi Noem: The South Dakota governor who won reelection in November has certainly cultivated a national profile, becoming a regular at conservative gatherings and donor confabs. But she hasn’t committed to a presidential run. “I’m not convinced that I need to run for president,” she told CBS in January.

Greg Abbott: The Texas governor who cruised past a 2020 presidential contender, former Rep. Beto O’Rourke, to win his third term in November is unlikely to make any official 2024 moves until his state’s legislative session wraps up at the end of May. He told Fox News in January that a 2024 run “is it’s not something I’m ruling in right now. I’m focused on Texas, period.”

Larry Hogan: The former Maryland governor is another Trump opponent. He told Fox News he is giving a 2024 run “very serious consideration.”

Chris Christie: The former New Jersey governor is one of several 2024 GOP prospects headed to Texas for a private donor gathering in late February, along with Pence, Haley, Scott, Sununu and Georgia Gov. Brian Kemp. Christie said on ABC earlier this year he doesn’t believe Trump could beat President Joe Biden in 2024.

Asa Hutchinson: The former Arkansas governor is a rare Republican from a deep-red state who has been willing to criticize Trump. Now weeks removed from office, he also doesn’t have the at-home responsibilities facing other governors. He told CBS that he’ll decide on a 2024 by “probably April.” He said he believes voters are “looking for someone that is not going to be creating chaos, but also has got the record of being a governor, of lowering taxes.”

Mike Pompeo: Trump’s secretary of state and the former Kansas congressman said during a tour for his new book, “Never Give an Inch: Fighting for the America I Love,” that he would decide on a presidential run in the coming months. He’s been among the Republicans most openly considering a run, traveling to early-voting states for more than a year.

Liz Cheney: The former Wyoming congresswoman who emerged as the foremost GOP critic of Trump’s lies about widespread election fraud lost her House seat to a Trump-backed primary challenger. She launched a political action committee last year and made clear she intends to try to purge the GOP of Trump’s influence. But what that means in the context of a potential 2024 bid is not yet clear.

Will Hurd: The former Texas congressman who represented a border district recently traveled to New Hampshire, an early-voting state, though it’s not clear whether or when he would enter the race. “I always have an open mind about how to serve my country,” he told Fox News.

Others to keep an eye on: Georgia Gov. Brian Kemp, who fended off a Trump-backed primary challenge on the way to reelection last year, has added political staffers and is sometimes mentioned as a vice presidential prospect. Florida Sen. Rick Scott and Missouri Sen. Josh Hawley have both said they will not run for president in 2024 — but things can change, and both had also taken steps to build their national profiles. Trump’s former national security adviser John Bolton has teased a run as a Trump foil.

Here are the Republicans considering 2024 presidential runs