The New Hampshire primary is all about the over-under, the percentage that determines whether Mitt Romney has exceeded, met, or failed to meet expectations.

The game, of course, is who gets to set those expectations.

Here are the early lines from some prominent political bookmakers;

DNC chair Debbie Wasserman Schultz (via AP):

“If Mitt Romney doesn’t get over 50 percent on Tuesday here, being a former governor of the state right next door and having a family home here, then there’s something seriously wrong,” said Democratic National Committee Chairwoman Debbie Wasserman Schultz told the Associated Press.

Romney strategist Stuart Stevens (via Michael Barone)::

“It’s mathematically impossible to win 40% in this field of candidates.” So Stuart Stevens, Mitt Romney’s chief political consultant, told me yesterday. This is part of the expectations game: Romney was running above 40% in New Hampshire polls in the days just after the Iowa caucuses but is now at 38% in the realclearpolitics.com average of recent polls, which includes the most iteration of each tracking poll and other polls taken in January. Stevens obviously wants to avoid the Maria Carrier effect, named after Edmund Muskie’s New Hampshire coordinator in the 1972 Democratic race, who said publicly that anything less than 50% for Muskie (who was from next-door Maine) would be a defeat. So when Muskie beat George McGovern 46%-37%, that was widely treated as a defeat—and McGovern went on to win the nomination.

(For a comprehensive historical overview, see NPR’s political junkie Ken Rudin.)

New York Times numberologist Nate Silver for the tiebreaker:

See you at the exit polls.