Public Policy Polling’s latest Iowa poll finds President Barack Obama ahead of four potential Republican opponents among 1,077 Iowa voters surveyed between January 7 and 9.

Yesterday’s release showed Mike Huckabee and Mitt Romney as the leading Republicans in the early caucus race for 2012, and if the election were today, those two are the only ones who would give Obama a bigger run for his money than McCain did two years ago. Obama tops Huckabee by a slender 47-43 margin, and Romney by 47-41. But against Newt Gingrich, he would prevail, 51-38, and by 53-37 over Sarah Palin.

The difference comes with independents, who make up a full quarter of the electorate, with Democrats and Republicans splitting the rest evenly. Obama has a significant party- unity advantage against all four Republicans, taking 86-91% of his own party and holding each of them to 67-79% of the GOP. But while he leads with unaffiliated voters by a 49- 34 margin over Gingrich and 49-38 over Palin, he actually trails Huckabee, 41-42, and leads Romney only 40-38. Huckabee and Romney do also hold Obama’s crossover support down. While he takes 13% of Republicans to Gingrich’s 5% of Democrats and 17% of Republicans to Palin’s 6% of Democrats, the split against Huckabee is only 10-7, and 11-9 against Romney.

Click here for the summary and here for the full polling memo (pdf). The poll’s margin of error is plus or minus 3 percent. PPP found 50 percent of Iowa respondents approved of Obama’s performance as president, while 43 percent disapprove. Tom Jensen commented, “When you combine Obama’s relative popularity in the state with the GOP field’s lack of appeal, it looks like things are going to have to get a lot worse for the President over the next 22 months to send Iowa back into the red column.”

I wouldn’t be too sure about that. If the unemployment rate stays roughly the same or inches up, and the Republicans nominate someone without high negatives like Gingrich or Palin, Obama will have to fight to hold Iowa. Huckabee has led several early polls of Iowa Republicans, but I think he would have trouble winning the nomination if he runs. If I were a GOP primary voter, I’d be looking for a bland senator or former governor who could essentially campaign as a generic Republican.

Incidentally, Iowa may become crucial to Obama’s path to victory in 2012. Reapportionment after the 2010 census took six electoral votes away from states Obama won, and several of the 2008 blue states are likely to go Republican next cycle. One path to exactly 270 votes would have the president winning all the states he carried in 2008 except for Virginia, Ohio, Florida, Indiana, North Carolina, and the second Congressional district in Nebraska.

UPDATE: The Cook Political Report lists Iowa as a tossup for the 2012 presidential race. The other states in that category are Colorado, Florida, Nevada, Ohio, Pennsylvania and Wisconsin.