New Insider Advantage poll of the Dem race in Iowa shows Hillary Clinton and John Edwards closing strong in a tight battle while Obama appears to be slipping:

Clinton 30 (+6 vs. last poll Dec 16-17)
Edwards 29 (+3)
Obama 22 (-5)

Overall, Clinton now leads by 1.8% in the RCP Average for Iowa.

Also good news for Edwards: among those currently planning to support another candidate, 62% identify him as their preferred second choice, only 21% choose Clinton and 17% Obama.

Taking these second choice preferences, Insider Advantage then applied the same reallocation formula they used in '04 which they say correctly a "comfortable win for John Kerry" - Edwards comes away with 41%, Clinton 34%, and Obama 25%.

Should we see a result like that, with Obama finishing in a distant third place 9 points behind Clinton and 16 points behind Edwards, it's hard imagine how Obama's candidacy wouldn't be mortally wounded. But this is simply one poll of many out there right now.

We'll have even more to chew on when the Iowa poll, seen as the Gold Standard in caucus polling, is released later this evening.