DES MOINES - The caucuses are 22 days away. Today in Johnston, Iowa just northwest of downtown Des Moines, the Republicans presidential candidates will gather for the last major debate before Iowa voters go to caucus. The Democrats will be in town tomorrow; same time, same location. Here's a quick primer on the debate

Where Things Stand
Huckabee has stormed to a huge 10.4% lead in the RCP Average for Iowa and while it's possible Iowa voters could fall out of love with Huckabee just as quickly as they've fallen in love with him, it seems unlikely. With the exception of Ron Paul, every other candidate in the field has seen their support tail off in the last few weeks as Huckabee has gobbled up support across the board.

What to Expect
Mitt Romney launched the first negative ad of the cycle this week, hitting Mike Huckabee on illegal immigration, so you can expect Romney to continue his direct assault. Huckabee effectively parried Romney on the issue two weeks ago in the YouTube debate, watch to see if he can do it again.

Keep an eye on Fred Thompson. Thompson has said he needs to finish at least third in Iowa, and given everyone else's weakness in the polls, there's an opportunity for Fred to separate himself and solidify a 3rd place standing with a strong debate performance. Thompson would like to bring Huckabee back down to earth without helping Romney, so expect Fred to train his fire on both this afternoon. He'll probably also take a whack or two at Rudy, who is running even with him in the polls and would also like to sneak in for a 3rd place finish.

Rudy will do whatever he can to help Mike Huckabee keep his boot on Romney's throat. The worse Romney loses in Iowa, the more damaged he will be heading into New Hampshire, where Giuliani is running a close third and trying to make a very strong showing. Ditto John McCain.

Add it all up and we should expect to see another round of sharp exchanges between candidates, most of which will involve Mitt Romney. We'll have to see whether today's debate changes anything, but given the location and the proximity to caucus day, it's a fairly important day for the top tier candidates to have a good showing and, most importantly, not to make a big mistake.