(AP) -- Donald Trump said he didn't have to win; Hillary Clinton didn't know whether she could. Marco Rubio said he was ready to lead the country; and Bernie Sanders said "don't jinx me" about predictions of a victory on Tuesday.

Only two days before New Hampshire's first-in-the-nation primary, candidates in both the Democratic and Republican races tried to lower expectations for the second contest on the election calendar and pitch ahead to South Carolina and Nevada, more diverse states where voters next get their say.

On the Democratic side, New Hampshire favorite Sanders and Clinton -- a narrow winner last Monday in Iowa -- have a long road ahead. Among Republicans, Texas Sen. Ted Cruz has Iowa in his column, Trump looks for a first win in New Hampshire, Rubio is working to maintain momentum after a close third in the caucuses and rivals such as New Jersey Gov. Chris Christie, Jeb Bush and John Kasich are banking on a solid showing Tuesday to propel their campaigns forward -- and avoid pressure to quit the race.

"I know I'm behind," Clinton, who trails Sanders in New Hampshire, said on CNN's "State of the Union." Asked if she can win, Clinton answered, "I don't know."

Republican Trump continued to insist on Sunday that he came in first in Iowa. Whether or not he wins New Hampshire as the polls suggest, Trump says his campaign will continue.

"I don't think I have to win it," Trump said on CNN of Tuesday's vote.

Bush, Florida's former governor who came in sixth in Iowa with 2.8 percent of the vote, insisted his campaign would continue regardless of the results in New Hampshire.

"Wednesday morning, I have my first event in South Carolina, and we're scheduling the Nevada trip, too," Bush said on Fox News Sunday.

Rubio, meanwhile, stuck to the talking points on Sunday that drew criticism during his uneven performance Saturday night. Christie, in particular, pilloried Florida's junior senator. Rubio repeatedly answered questions Saturday and Sunday by saying President Barack Obama is intentionally trying to change the country to suit an agenda.

"It's what I believe," Rubio said on ABC's "This Week." "It's what I'm going to continue to say, because it happens to be one of the main reasons why I am running."

Rubio's uneven performance on Saturday night could hurt his bid to emerge as an alternative to Trump and Cruz. Rubio has sought to appeal both to mainstream Republicans and those eager to upend the status quo. But his rivals, particularly Christie, have been blistering in their criticism of what they see as his slim qualifications to serve as commander in chief.

"You have not been involved in a consequential decision where you had to be held accountable," Christie said. "You just simply haven't."

Christie has built his closing argument around his criticism of Rubio, and he kept up that approach on the debate stage. He accused the senator of being a candidate governed by talking points -- then pounced when the senator played into his hands by repeating multiple times what appeared to be a planned response to criticisms about his qualifications.

"That's what Washington, D.C., does," Christie said. "The drive-by shot at the beginning with incorrect and incomplete information and then the memorized 25-second speech that is exactly what his advisers gave him."

Rubio wavered in defending his decision to walk away from the sweeping immigration bill he originally backed in the Senate -- perhaps the legislation he's most closely associated with -- and said he wouldn't pursue similar legislation as president.

"We can't get that legislation passed," Rubio said of the bill that would have provided a pathway to citizenship for millions of people in the United States illegally. The senator found his footing later in the debate when outlining his call for more aggressive action to fight the Islamic State group and emphasizing his anti-abortion stance.

Cruz drew heavily on the support of evangelical voters for his victory in Iowa. But he's faced criticism for messages his campaign sent to voters ahead of the caucuses saying rival Ben Carson -- another favorite of religious conservatives -- was dropping out and urging the retired neurosurgeon's supporters to back him instead.

Cruz apologized for his campaign's actions Saturday, but not before Carson jabbed him for having "Washington ethics."

Those ethics, he said, "say if it's legal, you do what you do to win."

Trump was back on the debate stage after skipping the last contest before the Iowa caucuses. He sought to refocus on the core messages of his campaign, including blocking Muslims from coming to the U.S. and deporting all people in the country illegally, all while maintaining he has the temperament to serve as president.

"When I came out, I hit immigration, I hit it very hard," Trump said. "Everybody said, 'Oh, the temperament,' because I talked about illegal immigration."

Kasich, who has staked his White House hopes on New Hampshire, offered a more moderate view on immigration, saying if elected president, he would introduce legislation that would provide a pathway to legalizing immigration status, though not citizenship, within his first 100 days in office.

The debate began shortly after North Korea defied international warnings and launched a long-range rocket that the United Nations and others call a cover for a banned test of technology for a missile that could strike the U.S. mainland.

Asked how he would respond to North Korea's provocations, Bush said he would authorize a pre-emptive strike against such rockets if it was necessary to keep America safe. Cruz demurred, saying he wouldn't speculate about how he'd handle the situation without a full intelligence briefing. And Trump said he'd rely on China to "quickly and surgically" handle North Korea.

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Associated Press writer Holly Ramer in Concord, New Hampshire, contributed to this report.

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