Bye-bye, Muscatine. Hello, Laconia.

Candidates in the already unpredictable and extraordinary presidential race will leave behind the frozen farmland of Iowa and descend on unseasonably warm New Hampshire Tuesday for a frenzied weeklong sprint to the primary.

Both Republican and Democratic contests have defied predictions for months, and veteran operatives say the next week could continue to upend convention. New Hampshire voters are notoriously late deciders in the presidential primary, and independents can switch between the Democratic and Republican contests, injecting an added element of uncertainty.

The vote will once again give New Hampshire outsized influence in shaping history.

For the next week, virtually no one in the state will be able to avoid the onslaught of rallies, bus tours, negative mailers, and television attack advertisements. Within hours of the end of the caucuses, nearly every presidential candidate will enter New Hampshire’s borders, unleashing armies of staff and volunteers to blitz voters’ phones and knock on their doors.

“For the next eight days you are the most powerful people in the world because the American presidency is the single most important job in the world,’’ Governor Chris Christie of New Jersey told a crowd in Hopkinton on Monday.

In the volatile Republican contest, at least four candidates — Senator Marco Rubio of Florida, former Florida governor Jeb Bush, Governor John Kasich of Ohio, and Christie — will be fighting to emerge as the main alternative to ­businessman Donald Trump and Senator Ted Cruz, popular outsider candidates who together captured about half of the GOP vote in Monday’s Iowa caucuses.

Rubio may have the strongest shot at laying claim to the title of establishment favorite after his suprisingly strong finish in Iowa.

Bush, Kasich, and Christie were already campaigning in New Hampshire on Monday after skipping the caucuses. Kasich has said that a poor finish in New Hampshire could prompt him to drop out of the race, and Bush has similarly staked much of his political fortune on the state.

“The reset has started as of tonight,’’ Bush told the crowd at the Alpine Club in Manchester, adding, “Next Tuesday, we’re going to surprise the world.’’

New Hampshire’s primary could be pivotal for Trump as well after his disappointing finish in Iowa. The bombastic businessman has led GOP polls of New Hampshire since the summer, although his campaign only recently assembled a traditional get-out-the-vote operation for the primary.

The first-in-the-nation primary has often produced unexpected results, mostly thanks to the state’s large portion of independent voters. More than 40 percent of the state’s voters can pull either party’s ballot on Feb. 9, adding unpredictability to the contest, especially the large field of Republican candidates.

“It’s as intense as anything I’ve seen up here,’’ said Tom Rath, a former state attorney general who has been involved in New Hampshire Republican politics for more than three decades. “I don’t think anybody would be confident to pick who’s going to win this thing now.’’

Polls show there is room for any of the candidates to gain ground on the GOP front-runners. While just 8 percent of likely Republican voters in New Hampshire were undecided in a UMass-Lowell/7News poll released on Monday, 42 percent said they could change their mind over the next seven days.

Rath said all of the candidates will be fighting to persuade those wavering voters.

“Right now, the real question is, can somebody in that group break out?’’ said Rath, who supports Kasich. “Is there somebody who can consolidate that middle, or is it going to stay splintered? That’s the overarching tactical situation here.’’

Wayne McDonald, the chairman of Christie’s campaign in New Hampshire and a former chairman of the state GOP, lamentedthat it has been so difficult for any of them — even those who spent more time courting voters in living rooms, veterans’ halls, and high school auditoriums — to gain traction against Trump.

But, with a glimmer of optimism, he added, “I don’t see any reason why we can’t continue to fight for second place, frankly.’’

In the increasingly contentious Democratic contest, Bernie Sanders — dismissed nine months ago as a socialist gadfly — continues to holds a sizable lead over Hillary Clinton, fueled by massive support from young voters.

“At this point, none of us knows what’s going to happen,’’ said Kathy Sullivan, a Clinton supporter and Democratic National Committeewoman from New Hampshire. “So many people make their minds up in the last week.’’

Another Clinton supporter, veteran Democratic political operative William Shaheen, downplayed expectations for Clinton’s campaign, saying that it was not vital for her to win the New Hampshire primary because she has the organizational strength to beat Sanders in South Carolina, Nevada, and the flurry of states ahead.

“She’s got the long game,’’ said Shaheen, the husband of US Senator Jeanne Shaheen. “No matter what happens, she’s going to continue to go.’’

New Hampshire has, historically, been friendly territory for the Clintons.

In 2008, Hillary Clinton, after losing the Iowa caucuses to Barack Obama, roared back into contention in New Hampshire and won the primary. And in 1992, Bill Clinton scored a strong second-place finish in the primary that earned him the nickname “the Comeback Kid.’’

On Tuesday, Bill Clinton is scheduled to speak at two rallies for his wife’s campaign, in Nashua and Laconia. Sanders plans to hold two of his own rallies, in Keene and Claremont.

“It’s going to be crazy,’’ said Sullivan, who pointed out that, in addition to the candidates, and their volunteers, the primary will draw national and international media attention and political tourists looking for a close-up view of the action. “It’s the political center of the universe for the next week,’’ she said.

Jim O’Sullivan and Sarah Schweitzer of the Globe staff contributed to this report. Michael Levenson can be reached at mlevenson@globe.com. Follow him on Twitter @mlevenson.