A national poll taken earlier this week shows Newt Gingrich leading Mitt Romney 38-29% with Rick Santorum 3rd at 18% and Ron Paul at 12%.

Gingrich scores very well with Tea Party voters and those who identify themselves as "strong conservatives" but gets massacred in a head to head matchup with President Obama by 18 points:

MSNBC:

Newt Gingrich leads Mitt Romney among Republicans, but he is the weakest of the Republican candidates tested against President Obama, according to an NBC News-Wall Street Journal poll released Thursday evening.

Gingrich leads Romney 37 percent to 28 percent nationally among registered Republicans likely to vote in the primaries; Rick Santorum is in third with 18 percent, and Ron Paul is fourth with 12 percent.

Gingrich has built its advantage by consolidating the heart and soul of the Republican Party: very conservative voters, the South and the Tea Party.

Though Gingrich is the preferred candidate of GOP primary voters, he performs the worst of all Republican candidates tested against Obama, including Santorum.

"Gingrich is Goldwater," said Democratic pollster Peter D. Hart, who conducted the survey with Republican pollster Bill McInturff. "In the general election, Gingrich not only takes down his ship, he takes down the whole flotilla."

I think the perception among GOP office holders that Gingrich would be poison at the top of the ticket will haunt him throughout the primaries. The down ballot races are going to be critical - especially the senate contests where the GOP has an excellent chance of winning control - and the fact that the Democrats have targeted 75 House seats and have an enormous war chest will play into fears by GOP congressman that Newt will take them down with him.

Romney is a loser against Obama as well, but with a much more manageable deficit of 6 points. Once again, GOP voters are going to be asked to vote with their heads and not their hearts in choosing Romney over Gingrich.