From the Des Moines Register:

Meet Iowa’s most popular 2012 GOP presidential prospects: Mitt Romney, Sarah Palin and Newt Gingrich. Others though, aren’t as popular. That means if Indiana Gov. Mitch Daniels, South Dakota Sen. John Thune or others have eyes on Iowa’s leadoff caucuses, they have a lot of baby kissing and handshaking to do.
According to The Des Moines Register’s latest Iowa Poll, 62 percent of Republicans who identified themselves as likely to vote in this week’s primary election are very or mostly favorable toward Romney. Palin follows, with 58 percent very or mostly favorable about her, with Gingrich at 56 percent,In contrast, 80 percent say they don’t know enough about Daniels to have a favorable or unfavorable opinion, 71 percent say they’re not sure how they feel toward Thune and 53 percent are unsure about Minnesota Gov. Tim Pawlenty.
The poll measures favorability, not preference. Lots can and will happen before serious presidential caucus campaigns launch next year that will wilt favorability and pump new candidates onto the list.