Ron Paul, the once-forgotten presidential candidate, is picking up steam in Iowa and now appears poised to overtake frontrunner Newt Gingrich, according to a new survey released today from the left-leaning Public Policy Polling.

The poll finds support for Gingrich has slipped to 22%, with Ron Paul just behind with 21%. Mitt Romney trails in third place with 16%.

That's a five-point drop in favorability for Gingrich, who has raced to the top of the Republican presidential field over the past month. PPP found Gingrich's favorability numbers have fallen 19 points over the past week.

Meanwhile, support for Paul is on the rise, particularly among younger voters and voters who identify themselves as "new." Among likely caucus-goers under age 45, Paul leads Gingrich 30-16. The numbers are nearly flipped for caucus-goers over age 45.

But what Paul's fans lack in age and experience, they make up for in enthusiasm — 77% of Paul supporters say they are definitely going to vote for him, compared to 54% for Gingrich.

Interestingly, Romney's support is also stronger than Gingrich's in Iowa, despite Romney's relative absence from the state this fall — 67% of Romney supporters say they will definitely be voting for him.

In fact, there is strong evidence that Romney actually could have been a major factor in Iowa this year, if he had not stayed away from the state. As PPP notes, only 44% of Romney's 2008 supporters plan to vote for him this time — which means if he had just managed to keep his support from last time, he would be leading in Iowa by now.

The PPP survey finds the rest of the field largely unchanged. Michele Bachmann comes in fourth with 11%, down from 13% last week. Rick Perry stayed stagnant at 9%, apparently unaffected by his controversial gay marriage/war on Christmas ad last week. Rick Santorum came in with 8%, while Jon Huntsman rounded out the field with 5% support.