The Republican candidates for President assemble tonight in Iowa for a debate, just two days before the Iowa Straw Poll and the expected entrance into the race of Gov. Rick Perry of Texas.

Two months ago in New Hampshire, the GOP hopefuls used their debate to basically introduce themselves to voters, opting more for a unified voice against President Barack Obama and Democrats, as frontrunner Mitt Romney escaped unscathed.

This time, Romney may get a bit more flak from his competitors, who know the number of days is rapidly dwindling for them to make into the top tier of candidates and to try to become the Alternative To Mitt.

For me, the biggest memory of the Manchester, New Hampshire debate in June was the decision of former Minnesota Gov. Tim Pawlenty not to go on the attack against Romney.

Two days earlier, Pawlenty had derided the federal health reform law as Obamney Care, charging the Obama plan was much like one that Romney had backed as Governor of Massachusetts.

But when offered up a hanging curveball on a platter at the debate to criticize Romney, Pawlenty failed to pull the trigger, and since then, his candidacy has struggled.

That same night, Rep. Michele Bachmann (R-MN) made the news that she was jumping into the race. While Pawlenty's star was tarnished, Bachmann jumped way up in the polls and quickly raised gobs of money. She could get some flak tonight as well.

For the others in the race, tonight is important for different reasons. Jon Huntsman is a perfect example - like Pawlenty, Huntsman has struggled in recent weeks, so this will be the former Utah Governor's chance to introduce himself on a national basis.

Others looking to claim some momentum include businessman Herman Cain, who used a debate in South Carolina to jump out of the field earlier this year, but has spent much of the last few months conducting his campaign from his home base in Atlanta.

Only in the last few weeks has Cain re-emerged on the hustings to meet with voters. Along with the Iowa Straw Poll, tonight is his chance to add some juice to his White House bid.

Others looking for a spark in coming days include Newt Gingrich and Ron Paul, though both are fully expected to keep their White House bids going no matter what happens tonight.

Of course, one person won't be at the debate, but may scoop up a majority of the headlines in coming days, and that is Gov. Rick Perry of Texas.

All signs indicate that he may announce his candidacy this weekend during a conservative gathering in South Carolina and then jump right onto the campaign trail the next day in Iowa.

Many people in Washington think Perry has the chance to enter this race and immediately become one of the top tier candidates.

And just as Michele Bachmann made life more difficult for Paul, Gingrich and Cain, Rick Perry may only double the weight on their shoulders by stepping into this race.

But as everyone knows, it just takes one snappy exchange, one moment of electricity to suddenly change your fortunes.

That's why they hold these debates, to winnow out the field. And tonight, we take another step down the road to the 2012 race for the White House.

In September, there are a pair of debates in Florida, one in Tampa on September 12 and one in Orlando on September 22.