Nikki Haley is now the top GOP alternative to Trump, but her window to maintain momentum is narrow. Can she pull it off?

• In recent weeks, ex-S.C. Gov. Nikki Haley has gained real momentum for her White House campaign.
• But polling bumps can come and go, and she'll have to prove her mettle under a brighter spotlight.

As former UN ambassador Nikki Haley has campaigned for president across the early-nominating states, she has touted a message of generational change, seeking to appeal to Republicans from across the ideological spectrum.

After months on the ground, Haley has finally found her sweet spot, largely overcoming Florida Gov. Ron DeSantis as the top alternative to former President Donald Trump. She's seen a substantial bump in her poll numbers, notably in Iowa and New Hampshire.

She won't be able to rest on her laurels, though, as her window of opportunity for toppling Trump in the primaries will be quite narrow, even with her mega endorsement from the Koch-aligned Americans for Prosperity Action. There's a long trail of insurgent presidential candidates who have seen their fortunes rise, only to falter weeks later.

What makes Haley's path so tricky?

A look back

In the lead-up to the 2016 Republican primaries, it was former Florida Gov. Jeb Bush who was seen as the presidential frontrunner. He was backed by the GOP establishment and was a scion of one of the most prominent political families in modern US history.

But then came Trump, who flipped the script when he entered that year's GOP contest.

Suddenly politicians like Bush, Florida Sen. Marco Rubio, and Texas Sen. Ted Cruz scrambled to deflate Trump's momentum, as the businessman quickly reeled in conservative base voters who had grown disenchanted with traditional GOP candidates.

After Bush's candidacy fell apart, Rubio and then Cruz were seen as the next big hopes to block Trump, but the senators were unable to stop him on Super Tuesday and in later contests and eventually suspended their campaigns. It's a fate that Haley is looking to avoid.

In 2020, Democrats dealt with a unique situation where the party's presumed frontrunner, Joe Biden, jumped into the race after then-California Sen. Kamala Harris and Massachusetts Sen. Elizabeth Warren had already launched their bids and were gaining steam.

But Harris' bid eventually fell apart before Iowa, and Warren underperformed in the early primary states. Biden was able to hold on, though, even as he was soundly defeated in the Iowa and Nevada caucuses, as well as the New Hampshire primary.

Despite Vermont Sen. Bernie Sanders' wins in New Hampshire and Nevada and Pete Buttigieg securing the largest delegate haul from Iowa, neither candidate was able to translate those victories to sustained momentum. Buttigieg was often called the future of the party and had gained substantial voter interest in Iowa, but he was unable to retain that support in later contests.

Biden went on to easily win South Carolina, and by Super Tuesday, virtually every Democrat still in the race, including Buttigieg and Warren, rallied behind the former vice president. Sanders soldiered on until April, but by then, it was clearly Biden's time.

Cutting through the noise

Haley has kept a busy campaign schedule in Iowa and New Hampshire, and she's now reaping the benefits with increased interest from voters and the Republican donor class. Several top GOP fundraisers are set to hold events for Haley in the coming weeks, and along with aid from the Americans for Prosperity super PAC, she'll have some financial juice for the first few primary contests.

But despite Haley's clear campaign positioning as an electable Republican who can attract independents and credibly face Biden, the GOP is still Trump's party.

The former president continues to lead in GOP polls in New Hampshire, Iowa, and Haley's native South Carolina, while also boasting national primary leads that have grown even more favorable for him since the beginning of the year.

Trump will likely launch broadsides against Haley soon, especially given the threat she could potentially pose to his candidacy in New Hampshire and South Carolina, so the next few weeks will be the biggest test for her campaign, as her standing could change by the end of the year.

When a candidate is suddenly in the hot seat, they can't blow it in the minds of voters. And Haley has two very current examples that are right before her.

Vivek Ramaswamy, the millennial entrepreneur who made waves during the first GOP presidential debate, overtook Haley in polling in the late summer and was battling it out with DeSantis as the leading non-Trump contender. But while Ramaswamy remains in the race, his numbers have dropped and he's no longer the GOP sensation who was at the tip of everyone's tongue.

DeSantis, whose campaign has so far been unable to bring down Trump's numbers despite his conservative record, averaged nearly 35% support in national polling in January, before he had even entered the race.

Per FiveThirtyEight, the governor is now averaging roughly 12% support nationally.