WEST DES MOINES -- "Iowa is the winnowing grounds," Kansas Senator Sam Brownback said in an interview today, explaining why he believes the state's straw poll matters. Pointing to candidates who dropped out in previous years after disappointing showings, Brownback speculated that "there are probably four tickets out of Iowa, max."

He plans on holding one of those tickets.

In recent months, Brownback has attacked former Massachusetts Governor Mitt Romney for changing positions on several issues, and his assault continued today. "He's outspending us 20-1, or whatever the number ends up being," Brownback said, concluding that Romney "should do exceedingly well" at the straw poll.

Asked to assess the chances, and given multiple opportunities to be critical of, former Arkansas Governor Mike Huckabee and Congressman Tom Tancredo, Brownback demurred and continued to target his fire on Romney.

By setting the bar for Romney's success high, Brownback hopes to convince others that Romney's over-spending shows a "weakness of message." Brownback said Romney's storied change of heart on abortion may have been understandable, "had it only been that issue." He pointed to taxes and gun rights as other areas ripe for charges of a Romney flip-flop, and he says he fears Democrats are just lying in wait for a Romney nomination. "Can't you just imagine the Democrat convention if he's our nominee," Brownback asked. "Can't you hear the speech now? Can't you hear the thirty speeches?"

Wearing a brown Brownback for President bracelet, in the fashion of distinctive yellow LiveStrong bracelets, Brownback seemed at ease after a get-out-the-vote rally at his West Des Moines headquarters. But explaining his own path ahead, Brownback acknowledged the fundamental uncertainty of the game he and Romney are playing: "In politics, a day's a long time, and a week is forever."

For Brownback and the rest of the candidates, the importance of the next long time -- that is, tomorrow -- cannot be overstated. Their tickets depend on it.