THE NATION - Straw poll may weed out the field - Today's Republican vote in Ames, Iowa, could spell the end of the run for some presidential candidates.

Yet the thousands of Iowans feasting on barbecued pork and casting ballots at the GOP festival carry real clout in the race for the White House.

By tradition, the Ames contest drives those who fare poorly to abandon their campaigns. For others, success can ease the pursuit of money and credibility.

The man with the most at stake is Romney, the former Massachusetts governor. He is the only major GOP candidate competing in the straw poll. The unabashed vote-buying contest lost some punch when former New York Mayor Rudolph W. Giuliani and Sen. John McCain of Arizona declined to participate.

Also skipping the event -- and further diminishing its luster -- is another big-name Republican: former Sen. Fred Thompson of Tennessee, who has been inching his way into the presidential race but technically remains on the sidelines.

So for Romney, anything less than a romp over the high-profile no-shows, whose names are still on the ballot, and lower-tier rivals would mark a humbling setback.

To avoid that, he has saturated Iowa TV with ads, held 53 voter forums in the state and mailed thousands of glossy brochures urging Republicans to vote for him in Ames. He has also chartered buses to haul supporters to the straw poll from every corner of Iowa.

"It could hurt him badly if he doesn't blow away the rest of this lesser field," said Hugh Winebrenner, author of "The Iowa Precinct Caucuses: The Making of a Media Event."

For the lesser-knowns, a poor showing in Ames could effectively doom their candidacies.

"Those who fail miserably are out of the race," said Chuck Laudner, executive director of the Iowa Republican Party. "That's just the coldhearted truth of it all."

Those most at risk -- generally viewed as former Gov. Tommy G. Thompson of Wisconsin, former Gov. Mike Huckabee of Arkansas and Brownback of Kansas -- are doing their best to grab the spotlight.

This morning, former Gov. Thompson will wheel into Ames, about 30 miles north of Des Moines, on his Harley-Davidson amid a posse of bikers. Huckabee will play bass guitar in his rock band, Capitol Offense. Brownback has assigned interns to splash into a water vat for entertainment; they will dangle over the tank on a bench that collapses when spectators toss a ball at a target and hit the bull's-eye.