Editor's note: John Avlon is a CNN contributor and senior political columnist for Newsweek and The Daily Beast. He is co-editor of the new book "Deadline Artists: America's Greatest Newspaper Columns."
(CNN) -- Game day is here -- the New Hampshire primary is under way.
Here are five things to look for that could determine the election outcome and the shape of the GOP field going forward:
• 1) What's Romney's benchmark for success? Mitt Romney's had a double-digit lead in New Hampshire polls for months. It's not surprising given his near-native status as a former governor of Massachusetts and as a Lake Winnipesaukee homeowner. And no statewide elected official from Massachusetts has ever lost the New Hampshire primary in an open field -- except Romney in 2008.
So what's the bar of success Team Romney needs to clear? I'd say 32% -- his share of the popular vote in 2008 when he came in second to John McCain.
In Iowa, Romney received six fewer votes than he did in 2008. If Romney can't exceed his popular vote count from four years ago in New Hampshire, it will be seen as another sign of his weakness as a front-runner -- a failure to attract new supporters and build his base. Remember, 75% of the primary voters still seem to want someone else despite Romney's organizational edge.
His support is strong on the streets of Manchester, with many voters I've spoken to citing his CEO experience, but the fact that New Hampshireites went to bed with the out-of-context sound bite "I like to fire people" in their heads won't help his effort.
• 2) Huntsman surge? Tuesday is D-Day for Jon Huntsman's campaign. He's been surging in the polls and raising record amounts of money in the wake of his strong debate performance Sunday. But is he surging too late? Huntsman has gambled on a principled campaign that is trying to revive the center-right tradition in the Republican Party.
He's an unapologetic fiscal conservative with an impressive executive accomplishment as governor of Utah. He's got unparalleled foreign policy experience as an ambassador in both Republican and Democratic administrations. And almost alone among these GOP candidates, he has refused to pander to the hyper-partisan tide polarizing American politics -- which makes him a strong general-election candidate.
These stands should make him a perfect candidate for New Hampshire Republicans and independents. The hit against him has been questions about how he will fare in the primary. New Hampshire voters will get to make that determination Tuesday. If they vote their conscience, Huntsman could exceed expectations and be a force in Florida and beyond. It helps Huntsman that New Hampshire voters will be going to the polls seeing that he tied Romney in midnight returns from the tiny hamlet of Dixville Notch.
• 3) How do independent voters break? New Hampshire is an open primary, meaning that independent voters -- who make up more than 40% of the local electorate -- can participate in the primary. More states should have open primaries because it leads to a more representative segment of the electorate and elevates more electable candidates. How independent voters break will determine who wins -- and, almost as importantly, who comes in second.
Right now Rep. Ron Paul and Huntsman are fighting for disaffected independents, pointing to the fault lines between libertarian-conservative-leaning independents and centrist independents. With a new Gallup Poll showing that independent voters now make up 40% of the national electorate -- an all-time high for that poll -- the importance of independent voters nationally in New Hampshire can no longer be ignored.
• 4) Paul's support. The "Live Free or Die" state should be a great fit for Paul, and my guess is that he will at least double his 2008 total, as he did in Iowa. Despite the libertarian impulses of this anti-tax free state, Paul only got 8% in the 2008 elections here. He'll have to do better than 16% to get in the top tier. But Paul's supporters are intense and increasingly organized. New Hampshire tea partiers could send a strong signal by supporting him. Unlike other candidates, he is playing a long game, able to raise money online and continue his campaign of ideas indefinitely, gaining delegates state by state and seeking to influence the convention and party platform.
. 5) Gingrich or Santorum? These two candidates seem to be fighting for fourth place, at least according to recent polls. They are already focusing their efforts on South Carolina, looking to establish themselves as the true conservative alternative to Romney.
Despite Rick Santorum's momentum out of Iowa, his social conservative beliefs don't play well in New Hampshire, the least religious state in the nation. His benchmark can be seen as Mike Huckabee's 2008 total of 11.5% and nearly 27,000 votes.
Gingrich has the added in-state benefit of The Union Leader's endorsement -- a conservative bellwether that pointedly chose him over Romney, beginning the Newt surge in November. A strong New Hampshire could bolster Gingrich's case as the most electable conservative alternative to Romney.
One final thing to remember as voting starts in New Hampshire -- the polls have been off in this state historically. In 2008, polls showed a Barack Obama win to be likely, but Hillary Clinton won the primary, giving her campaign a boost that ended up lasting through June. It's an independent-minded state, and voters take their civic responsibility seriously. They know the only poll that counts is on Election Day. Game on.
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The opinions expressed in this commentary are solely those of John Avlon.