GOP candidates face early test in 2012 campaign

And Pawlenty, trying to control expectations, predicted the results would show "momentum." He did not promise his supporters a win.

"Part of it is whether the message resonates, but the bottom line is you better be pretty well organized," Iowa Christian Alliance head Steve Scheffler said.

The straw poll has a mixed record of predicting the outcome of the precinct caucuses.

In 2008, Romney won the straw poll, but the big news was the surprising second-place showing of former Arkansas Gov. Mike Huckabee. Huckabee won the Iowa caucuses, but dropped from the race soon after. McCain, who eventually won the nomination, didn't compete in the straw poll and finished in 10th place.

Poor showings usually force some candidates, mostly those who are not well-known and are struggling to raise money, to abandon their bids, and that could happen this year, too.

GOP strategist Rich Galen called it "a winnowing process and that might happen to Pawlenty if he doesn't do well. It sort of serves as a filter to clean out the candidates who probably shouldn't be there in the first place."