Mitt Romney may be favored in the New Hampshire primary, but the state’s ballot may hurt the former Massachusetts governor’s bid to meet the lofty expectations that he carries into the contest.

Romney appears third from the bottom of the list of 30 candidates in the state’s Republican presidential primary. It’s a position likely to drag down Romney’s numbers, according to research by Stanford professor Jon Krosnick.

Ballot order can make a big difference, particularly when voters are undecided or conflicted headed into the polls. In 2008, for example, Krosnick estimated that Hillary Clinton gained at least 3 percentage points over Barack Obama in New Hampshire because her name was near the top of the ballot, his near the bottom. (Clinton won the primary by about 3 percentage points.)

The reason ballot order plays a large role, Krosnick explains, is a psychological process called “confirmatory choice.” When voters are undecided, they read down a list of names, with higher odds of selecting one they come across higher than lower. They may simply say “good enough” when they come to a satisfactory candidate.

The structure of this year’s Republican ballot is unlikely to tip Romney from his perch high atop the polls, but it could affect how well he does compared with pre-election polls. And it may have a significant effect on the other candidates vying for high finishes.

New Hampshire’s Secretary of State lists candidates in alphabetical order, starting at a random place. This year’s GOP ballot starts with Joe Story, runs from there through the alphabet, ending up at Rick Santorum.

Santorum is probably the biggest loser in the ballot order. Not only is he at the bottom of the list, but two candidates listed near the top may take some votes from him.

Those two candidates – Michele Bachmann and Herman Cain – have suspended their campaigns for the nomination but remain on the ballot, close to the top. Since Santorum has recently excelled among the same tea party conservatives who once flocked to Bachmann and Cain, the former Pennsylvania senator may suffer marginally as a result.

Who benefits this year?

At position 14, Newt Gingrich is tops among major active candidates. Next up is Jon Huntsman at spot 17.