I’m skeptical, especially if you count his Super PAC as part of his campaign. (And who doesn’t?) But the basic logic makes sense. If you depend heavily on a small-ish base of wealthy donors who are capped by law on how much they can give, then you’d better win early to grow that base before they’re all tapped out. If Santorum bumps him off in Michigan and Romney underperforms on Super Tuesday, it suddenly gets much harder for Mitt to lure big money with the promise of access to the eventual nominee.

Romney has proved unable to tap into the emotion-drived small-dollar contributions that helped power Barack Obama in 2008, and which fueled even his more Establishment rival, Hillary Clinton, this time four years ago when she too began to run out of big donors. The result: Republican fundraisers say that despite his success so far, they think Romney is fast approaching a wall, and that he will likely be forced to pay for the campaign out of his own deep pockets…

Over 82 percent of Romney’s haul from individuals in 2011 came in donations greater than $1000 —which doesn’t even include the larger donations to the SuperPAC that supports him, Restore Our Future. And as Rick Santorum stays in the game with a growing pool of small donors — to whom he can return for another $20 or $100 when the millions they’ve given him runs out — Romney’s campaign has launched an intense, late scramble for the cash to fend off his conservative challenger…

Three Republicans who work closely with Romney’s bundlers said they had begun to shift their focus away from the presidential campaign entirely.

“All the low-hanging fruit has been picked,” said a top New York finance industry donor and fundraiser who is currently neutral in the race and described Romney as “a Republican John Kerry running Hillary Clinton’s campaign.”

Follow the link for six different reasons why he’s having trouble. The obligatory caveat: Stories like this are self-fulfilling prophesies insofar as the worse the news gets for Romney, the more skittish his donors are likely to become about ponying up. It’d be easy for mischievous Republicans inclined towards Santorum or Gingrich to plant an extra seed of doubt in the media by pushing an angle like this — which is not to say that’s what’s going on here, but merely that it’s possibility. The big wrinkle in the narrative is that Romney’s donors can, of course, give unlimited amounts to his Super PAC, which is doing most of the heavy lifting for him anyway. His whole campaign is an exercise in making his opponents seem just a little bit worse/less electable than he is, and it’s the Super PAC and its negative ads that are chiefly responsible for doing that. As long as he’s got rich friends willing to give millions to Restore Our Future, he should be okay, and the richer and more generous they are, the fewer of them he needs. In fact, according to the WSJ, Newt’s billionaire backer Sheldon Adelson might end up cutting Romney a check purely in the interest of stopping Santorum. Evidently he thinks RS is too socially conservative; doubtless many libertarian-minded conservatives agree. If Santorum cements his status as a genuine threat for the nomination with a few more wins, Romney should get some new support from those voters plus donors who fear that RS can’t win the general election and needs to be stopped now. (See, e.g., the conservative media reaction to Gingrich after he won South Carolina.) In other words, the newly anointed “Not Romney” will turn Mitt into “Not Santorum” and then we’ll have a fight all the way to Tampa over which of these two candidates Republicans dislike least. Just like we’ve always dreamed.

Here’s Romney on “Fox & Friends” this morning feigning puzzlement as to why Palin would doubt his true-blue conservatism. “Living life tends to make you more conservative,” he says. Philip Klein’s response: “So he started ‘living’ at age 58?” Click the image to watch.