"See you on the 15th," Nikki Haley says in a tweet pinned to the top of her Twitter page.

That’s when the former South Carolina governor who served as ambassador to the United Nations during former President Donald Trump’s administration is expected to declare her candidacy for president, joining Trump as the only major Republicans to date to have launched White House campaigns.

Since Trump jumped into the presidential race in mid-November, it’s been a field of one in the hunt for the GOP nomination. But Haley’s entry — at an event in Charleston, South Carolina — could open the flood gates, with other likely Republican White House hopefuls launching their own campaigns in the weeks and months ahead.

"While there’s clearly been some reluctance to get in early, she’s setting herself apart and creating an opportunity for herself to define herself early, to establish her campaign," longtime New Hampshire based national Republican strategist Jim Merrill told Fox News.

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Nikki Haley

Former South Carolina Gov. Nikki Haley, who served as ambassador to the United Nations during former President Donald Trump's administration, speaks at the Republican Jewish Coalition (RJC) Annual Leadership Meeting in Las Vegas, Nevada, US, on Saturday, Nov. 19, 2022. (Ronda Churchill/Bloomberg via Getty Images)

"I expect that we’ll see other candidates get in soon, over the next few months, and that we’ll have a robust primary field," Merrill, a veteran of numerous GOP presidential campaigns, predicted.

While the presidential campaign is starting at a slower pace than in previous cycles, the action is starting to pick up.

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On the day Haley’s expected to launch her campaign, former Vice President Mike Pence will be in Iowa, the state whose caucuses kick off the Republican presidential nominating calendar. Pence, who’s made numerous stops the past two years in Iowa as well as the other early voting states of New Hampshire, South Carolina, and Nevada, is likely to launch a presidential campaign in the coming months.

MIke Pence in Iowa

Former Vice President Mike Pence headlines the annual Kaufmann Family Harvest Dinner, on Sept. 29, 2022 in Wilton, Iowa. The event attracted Republican officials, politicians, leaders, and activists. (AP )

Sen. Tim Scott of South Carolina, who pundits view as a potential presidential contender, heads to Iowa the following week as part of a listening tour that was first reported recently by Fox News.

While Trump remains the most popular and influential politician in the GOP and arguably the party’s top fundraiser when it comes to energizing the grassroots, the first three months of his latest White House bid have been anything but spectacular.

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Political pundits from both the left and the right torched his campaign launch, and he’s been criticized by Democrats and some Republicans for controversial actions and comments he’s made during the past couple of months. In the wake of a lackluster performance by the GOP in the midterm elections — when the party underperformed in what many expected to be a red wave election — Trump has also been blamed for elevating polarizing Republican nominees who ended up losing in November.

Donald Trump campiagn kick off in South Carolina

Former President Donald Trump speaks at a campaign event at the South Carolina Statehouse, Saturday, Jan. 28, 2023, in Columbia, S.C.  (AP)

While the former president was once the overall front-runner in the early 2024 GOP nomination polls, Florida Gov. Ron DeSantis has eclipsed him in some surveys over the past few months. Nearly ever poll indicates Trump and DeSantis as the favorites, with everyone else in the single digits.

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DeSantis, a former congressman, narrowly won his first election as governor in 2018 thanks in part to strong support from then-President Trump. But he saw his popularity soar among conservatives across the country the past three years, courtesy of his forceful pushback against coronavirus pandemic restrictions and his aggressive actions as a conservative culture warrior, going after media and corporations. 

The governor became a prolific fundraiser during the 2022 election cycle, hauling in over $200 million as he built a massive war chest with contributions from across the country. And his nearly 20-point victory over former Republican-governor-turned Democratic congressman Charlie Christ helped transform the one-time blockbuster battleground into a red state.

Gov. Ron DeSantis

Florida Gov. Ron DeSantis speaks during a news conference at Bill Baggs Cape Florida State Park, Thursday, Dec. 1, 2022, on Key Biscayne, Fla.  (AP Photo/Lynne Sladky)

DeSantis for over a year routinely dismissed talk of a 2024 White House race as he focused on his gubernatorial re-election. But he’s dropped plenty of hints of a possible presidential bid since his re-election victory speech in November. And as Fox News first reported, he’ll be publishing a memoir titled "The Courage to Be Free: Florida's Blueprint for America's Revival" later this month. Writing a book is a rite of passage for many potential and actual presidential candidates.

While sources in DeSantis’ wider orbit say any presidential campaign launch wouldn’t occur until late spring or early summer, after the end of Florida’s currently legislative session, Republican sources confirm to Fox News that the governor’s political team has already started reaching out and identifying operatives for a potential White House run.

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Merrill noted that "President Trump starts at the front-runner, but he’s not in the same position he was years ago. So, there’s an opportunity there and Haley’s the first to take advantage of it. And I’m confident that several others will in the weeks and months ahead."

Republican consultant David Kochel, a veteran of numerous GOP presidential campaigns in Iowa and nationally, emphasized that once someone else jumps into the race, "Trump’s going to turn on the guns and come after you and start to draw contrasts and find the right nickname."

In recent weeks Trump has trained his fire increasingly on DeSantis, and to a lesser degree Haley.

"Trump is best when he’s counter punching, when he’s drawing contrasts. So, denying him the direct conflict is also a way to starve him of oxygen.," Kochel said, pointing to the lack of a robust field to date.

Tim Scott

GOP Senator Tim Scott of South Carolina, speaks during the Republican Jewish Coalition (RJC) Annual Leadership Meeting in Las Vegas, Nevada, US, on Saturday, Nov. 19, 2022.  (Ronda Churchill/Bloomberg via Getty Images)

Among the others making moves towards launching a campaign or seriously considering a Republican presidential run are former Secretary of State Mike Pompeo, who’s currently on a book tour, now-former Govs. Larry Hogan of Maryland and Asa Hutchison of Arkansas, Govs. Chris Sununu of New Hampshire, Kristi Noem of South Dakota, and Glenn Youngkin of Virginia, former Gov. Chris Christie of New Jersey, and former Rep. Will Hurd of Texas.

Longtime GOP consultant and former New Hampshire attorney general Tom Rath noted that the White House race is "a battle for oxygen and attention," and emphasized that as of now both Trump and DeSantis are taking up nearly all the "oxygen and attention."

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He argued that "it’s hard for some of the others to emerge."

Merrill agreed that "Trump and DeSantis start out in an enviable position as the leaders of the earl primary. But I’m convinced there is room for other candidates to make a case and be there at the end. But to do that you got to get in and you’ve got to compete."