With just nineteen days until the Iowa Caucuses, tonight's gathering of major Republican candidates will be the final GOP debate before Iowa voters deliver the first important decision of the 2012 race for the White House, a debate that could result in some last ditch efforts by one or more candidates to make a big impression on voters in the Hawkeye State.

This evening's faceoff on Fox News is in Sioux City, a city of over 80,000 along the Missouri River in the northwest of Iowa; will we see fireworks like last weekend in a debate in Des Moines?

In that debate on ABC, Mitt Romney went after Newt Gingrich early, trying to contrast their careers, accusing Gingrich of being a lifelong politician.

"But our real difference, I believe, is our backgrounds," Romney said. "I spent my life in the private sector."

While Gingrich has said he won't get into any nasty back and forth with his opponents, he didn't take that shot sitting down.

"The only reason you didn't become a career politician is because you lost to Teddy Kennedy in 1994," Gingrich said.

In recent days, Romney has kept up a drumbeat of criticism against Gingrich, taking direct shots at the former Speaker in interviews and in repeated emails to reporters.

"Gingrich should follow his own advice and return the money he got from Freddie Mac," said one such missive on Wednesday.

One should also expect attacks on Gingrich from both Ron Paul and Michele Bachmann; in fact, Bachmann has taken to attacking both Gingrich and Romney in the same sound bite, lumping them together as unsuitable for conservative Republican voters.

Paul remains the wild card in Iowa, with what is reportedly a solid organization, some believe he could challenge for one of the top spots in Iowa - making his strategy in this debate all the more important.

One interesting note is that there are more and more rumblings in the press about whether Gingrich's poll numbers are starting to soften here in Iowa.

As I've discussed on the air in recent days, Gingrich is being hit hard with ads from Romney, Paul and outside groups linked to Romney.

Meanwhile, Gingrich does not have much of a media buy - so his message is being dwarfed.

Maybe Gingrich's message wins out.

Or maybe we're about to see another cycle in the GOP race.