No. 3: Will Huntsman be New Hampshire's Santorum?

Like Santorum, the former Utah governor failed to gain traction for most of the past year. He skipped Iowa and staked his campaign entirely on a good showing in New Hampshire to stay alive.

With 16 percent of support, Huntsman ranks third in the PPP New Hampshire survey, much higher than his low-single-digit showing in national polls.

His moderate position on social issues including his support for civil unions works well in New Hampshire, where same-sex marriage is legal.

But even with a top-three finish on Tuesday night, Huntsman's White House bid is still considered a long shot. He has weak campaign organizations beyond New Hampshire and his moderate message would be hard to sell to a GOP electorate more conservative than before.

No. 4: Will Paul upset New Hampshire with independents, young voters?

The 76-year-old Texan has become somewhat of a political rockstar. He runs strong among independents and young voters who share his anti-government and isolationist views.

In the Iowa caucuses, Paul received 44 percent of the vote among independents, and 48 percent of voters aging under 30.

The large amount of independents in New Hampshire, which account for more than 40 percent of the total electorate, would be an important asset for the libertarian-leaning candidate.

Paul's son, Kentucky Senator Rand Paul, predicted Monday that his father could emerge victorious in Tuesday's primary if there is a sizable independent showing.

"I think there's a remote chance we could pull an upset here if there is a large independent turnout -- if all of a sudden, in the last two days, independents said, 'We want to send a message, and we want to get out and vote,'" he said on the campaign trail in New Hampshire.

No. 5: Who's next to quit?

The New Hampshire primary, along with the Iowa caucuses, is not only a place for candidates to test the water of the presidential election but also to winnow the field.

Minnesota Congresswoman Michele Bachmann dropped out of the race after a poor showing in Iowa, where she was a favorite last summer.

A weak showing in Iowa also made Rick Perry to reassess his candidacy, though he backed away hours later to indicate he would press ahead into South Carolina.

So is there anyone to quit after the New Hampshire primary? Some analysts said Huntsman might do so if he falls out of the top three.

A candidate's dropping out might have important implications for the rest of the field. For instance, Bachmann's quit would benefit Santorum most, as the two candidates were competing for the same pool of GOP voters -- evangelicals and social conservatives.