"The main reason the Republican establishment overwhelmingly favors Mitt Romney over Newt Gingrich is that Romney stands a better chance of beating Barack Obama," says Jonathan Chait at New York. So it's a problem for Romney that "as the campaign goes on, this seems to be growing less true." A new Washington Post/ABC News poll shows that negative views of Romney have "spiked" over the past two weeks, from a net +4 favorability rating (39 positive/34 negative) to a -18 rating (31 positive/49 negative) — very similar to Gingrich's -22 rating (29/51). The shift is most notabe among independents, who went from generally liking Romney (41/34) to disliking him by a 2-to-1 margin (23/51). Democrats (21/62) and Republicans (58/32) have soured on Mitt, too. What's behind Romney's newfound unpopularity? Here, seven theories:

1. Voters are turned off by his wealth
Americans have long known that Romney is rich, but his just-released tax returns highlight just how much he earns from doing so little, says Peter Foster at Britain's Telegraph. Someone who rakes in $60,000 a day from personal investments is clearly "part of the elite – the '1 percent' that lives by different rules from ordinary Americans." But "the raw amount of money isn't really Romney's problem," says Chris Cillizza at The Washington Post. "It's the exoticness of his finances" — a Swiss bank account, money parked in Luxembourg and the Cayman Islands. "There is nothing more dangerous in politics than 'otherness,'" and Romney's fortune reeks of it.

2. And he's cagey about his fortune
Romney's big weakness is that "he squirms like a worm on a hook whenever someone points out his wealth," says Charles Blow in The New York Times. Gingrich has deftly exploited that in recent debates, getting Romney to make a point of "'not apologizing' for getting filthy rich" by buying and disposing of companies. These "non-apologies reek of guilt and shame, which in turn puts people's antenna up."

3. Romney has alienated Reagan Democrats
Romney's support has dropped among all voters, but it has plummeted among "blue-collar whites," says Greg Sargent at The Washington Post. That suggests his "wealth, privilege, low tax rates, and generally out-of-touch persona" are becoming a problem. "A smart candidate would use this fact and retool his message," at least acknowledging that Americans don't like "massive disparities of wealth," says Jamelle Bouie at The American Prospect. "But, like a petulant teenager, Romney has gone in the opposite direction," accusing critics of envy. Way to go, Romney, says Dan Riehl at Riehl World View. You've lost us the Reagan Democrats.

4. Being a venture capitalist turned out to be a liability
Voters started turning on Romney when his rivals started attacking a resume line Romney had touted as a selling point: His private-sector success at private equity firm Bain Capital. And no wonder, says AJ Strata at Strata-Sphere. Romney isn't a product of Main Street who worked his way up. He's a "corporate raider who made millions the easy way — the Haarvaaard way." That's a liability with Wall Street Occupiers and Tea Partiers. Romney's not a job creator, he's a vulture capitalist. "Vultures have their purpose in nature and economics, but they are not what someone wants in a national leader."

5. The inevitability gambit backfired
If I had to sum up Romney's growing unpopularity in one word, I'd pick "entitlement," says The American Prospect's Bouie. "From his refusal to engage his opponents for much of the primary, to his transparent pandering on virtually every issue under the sun, this sense of entitlement has carried over to every inch of his presidential campaign." Voters aren't stupid: They know when a candidate takes them for granted, and they much prefer to be seen as "supporters to be won, not obstacles to endure."

6. He can't handle his rivals' attacks
Romney's spiking unpopularity "coincides with a difficult period" on the trail, says Nate Silver at The New York Times. His GOP rivals have been drawing blood with "attacks against him that may resonate more with independent voters than among actual Republicans." That validates my long-held theory that Romney can't "withstand the types of attacks used by Ted Kennedy (Bain) and John McCain (lack of core convictions)," says William Jacobson at Legal Insurrection. Romney never went through the "withering assault and scrutiny" his opponents did last fall. Now that he is finally getting a taste, it's "showing up in polling."

7. Going negative hurt him
After losing big in South Carolina, Romney and his surrogates started "going far more negative on Newt Gingrich," calling him a "disgrace" who "embarrassed his party," says Doug Mataconis at Outside the Beltway. The problem is, "Romney isn't necessarily very good when he goes on the attack." Worse, this "Mad Mitt Beyond BlunderDome" routine is "most un-presidential and runs contrary to the finely crafted image his army of consultants have crafted for him," says Dan Riehl. When people ask for him to show more passion, they don't mean "angrily spewing slander."