Insider Advantage is out with a most interesting poll in Iowa, surveying both "likely" voters and also "highly likely" voters. On the Democratic side, among "likely voters" Edwards holds a 3.5% lead over Clinton and a 5.5% lead over Obama. But among the smaller group considered "highly likely" to participate in the January 3 caucus, Obama jumps to the top, though by a statistically insignificant margin:

Democrats
Obama 26.6
Edwards 26.0
Clinton 23.8
Other candidates 14.0
Undecided 9.5

Even more interesting is the follow up question, which asks those supporting another candidate who they'd switch their support to if their candidate fell below the 15% viability mark. The result should have the Edwards folks feeling pretty good:

Edwards 41.9
Obama 31.1
Clinton 27.0

Overall, Obama leads in the RCP Average for Iowa by 3.4%

On the Republican side, some good news for Mitt Romney. Though Romney trails Huckabee by about two and a half percent among "likely voters," he pulls into a three point lead among those considered "highly likely" to caucus:

Republicans
Romney 28.0
Huckabee 25.1
Thompson 10.8
McCain 6.9
Paul 5.5
Giuliani 5.1
Tancredo 3.7
Undecided 14.4

Overall, Huckabee still leads in the RCP Average by 8.0%.