This is a key week in the Republican nominating process, as a Thursday debate in Iowa will precede the Ames Straw Poll in that state this weekend, traditionally a test of grassroots backing, organization, and fundraising that historically has propelled unknowns to win the first-in-the-nation caucuses the following winter.

Mitt Romney, who won Ames in 2007, eventually lost the Iowa caucuses to Mike Huckabee, who finished a surprisingly strong second at Ames and never lost the momentum. This time around, Romney isn’t playing in the straw poll for that very reason.

Michele Bachmann, the Iowa frontrunner, needs to do well to maintain her image as a populist with wide Tea Party backing.

Tim Pawlenty, who has done over 100 events in Iowa but remains stuck in the single digits in polls, needs to at least exceed expectations and probably place in the top two to get any buzz heading into New Hampshire. Having predicated his whole candidacy on this state, a poor showing probably dooms his candidacy.

The Herman Cains and Ron Pauls of the world would need a breakout performance that jolts media perceptions of the viability of their candidacies to get anything useful out of the event.

Look for sharper contrasts than we’ve seen thus far in Thursday’s debate as the candidates jockey for the social conservative base that will likely determine the nominee to take on Obama next fall.