Gallup has some new polling numbers out that should be troubling to Mitt Romney. They suggest that a very sizable number of moderate to liberal Republicans see Newt Gingrich as an “acceptable” nominee for the Republican Party to field this fall.

Since these voters are supposed to represent Romney’s base of support, this would seem problematic to Romney: They don’t see Gingrich as self-disqualifying.

First, the toplines. Gallup finds that 64 percent of Republicans and GOP leaners see Gingrich as an “acceptable nominee for president from the Republican Party.” Only 34 percent — barely more than a third — see Gingrich as “not acceptable.” Romney’s numbers on this question are lower, at 54-41.

Dig into the ideological breakdown and it gets even more interesting. Nearly half, 48 percent, of moderate or liberal Republicans see Gingrich as acceptable. That’s only three points less than the number of them who see Romney as acceptable, which is at 51 percent. By contrast, the number of Tea Party Republicans who see Gingrich as acceptable is 24 points higher than the number who see Romney as acceptable. Among conservative Republicans, that number is 13 points. Though Romney does pretty well with both those groups, Gingrich does far better among his voters than Romney does among his.

As Ronald Brownstein has observed, the GOP primary is essentially unfolding on two tracks. There’s the battle for moderate Republicans who care more about electability and about reviving the economy; and the battle for the Tea Party/populist wing of the party, which wants a true ideological conservative who will go after Obama with a sledge hammer. The thinking has been that ultimately, the moderate wing will ultimately not be willing to accept someone like Newt — he’s undisciplined, has much baggage for a general election, and is an aggressive, overly partisan figure — while the Tea Party wing will ultimately make its peace with Romney because he has the best chance of beating Obama.

These new Gallup numbers raise the possibility that Newt may be clearing the threshold with many of the voters who are supposed to find a candidate like him unacceptable. Romney is expected to mount a fierce negative campaign against Gingrich to drive up his negatives among GOP primary voters, but he’s running out of time.