Until now, Mitt Romney’s presidential candidacy has been propped up by two perceived strengths: his knowledge of economic matters and the belief that he’d be the strongest general-election competitor to President Obama.

His experience in the private sector and as the turnaround artist for the 2002 Winter Olympic Games underscores the economic argument, and his centrist ideology and tenure as Massachusetts governor informs the belief that he’d be a general-election candidate who could appeal to crucial independent voters and centrist Democrats.

But his electability argument seems to be cracking before our very eyes, calling into question one of the fundamental rationales for his candidacy.

A Rasmussen Reports survey, released Monday, showed that 49 percent of likely GOP primary voters now think Newt Gingrich has the best chance of beating Obama, while only 24 percent say Romney has the best shot. 

That’s a dramatic reversal. 

Just one month ago, an ABC survey showed that 33 percent of GOP voters thought Romney was most electable, and just 5 percent thought Gingrich had the best chance against Obama. In other words, in just one month, Gingrich has seen a 53 percent gain on Romney in electability.

The ironic thing is that this perception of superior electability isn’t borne out by polls actually pitting Obama against the two GOP front-runners.

For example, Rasmussen, a GOP-leaning pollster, shows Romney performing 8 percent better than Gingrich in a general election. 

More compellingly, a Purple Strategist poll of swing states has Romney performing better than Gingrich against Obama in three of four regions of the United States. Gingrich, for example, only managed a tie against Obama in Southern swing states, while Romney bested Obama everywhere else.

But if Romney has been polling better against Obama, Gingrich seems to have an electability card in his pocket that the former Massachusetts governor doesn’t: Republicans are salivating at the prospect of Gingrich taking Obama on in a debate. 

Gingrich’s gift for assembling compelling arguments and presenting them as clear contrasts seems particularly relevant when trying to oust an incumbent. 

To these Republicans, numbers are fairly meaningless. They’ve seen Gingrich rise from the ashes to the top of the GOP heap, and why couldn’t he do the same in the general election? They have a point. If Gingrich debated his way past Romney and everyone else, why couldn’t he do the same to Obama?

Further, Gingrich has promised a vigorous polemic challenge to Obama. The former House Speaker told Fox News last month that if he’s the nominee, he’ll challenge the president to seven debates instead of the traditional three, and that if Obama refuses, he’ll track the president’s every footstep until he gives in.

But there’s something far deeper than just debates at the root of Gingrich’s rise and Romney’s slide. Many Republicans are starting to look at who’s actually won, in the past, to determine who might win in the future.

And, in Gingrich, Republicans see the mastermind of one of the most remarkable and transformative elections in their lifetimes — the Republican Revolution of 1994, when Gingrich engineered a historic congressional takeover.

Romney, on the other hand, doesn’t have such a great track record. 

As Gingrich gleefully noted in last week’s debate, Romney lost to then-Sen. Edward Kennedy (D-Mass.) by 17 percent in 1994, and in the 2008 presidential primary, he came in third overall, being unable to defeat an establishment candidate whom conservatives disdained (John McCainJohn Sidney McCainGOP strategist donates to Alabama Democrat Meghan McCain knocks Bannon: 'Who the hell are you' to criticize Romney? Dems demand Tillerson end State hiring freeze, consult with Congress MORE) and an outsider the establishment disdained (Mike Huckabee).

And despite having superior finances and organization this time around, Romney hasn’t been able to consistently crack 30 percent in GOP polling.

There’s another wrinkle to the Romney electability argument that’s come to the forefront over the past month: His personal wealth, while always subject to scrutiny, is fast becoming a severe liability to his campaign.

In a debate over the weekend, he played into Democrats’ efforts at painting him as rich and out of touch by challenging Rick Perry to a $10,000 bet.

The reaction was instantaneous and negative. Republicans groaned at his tone-deaf comment in these economically ravaged times, while Democrats shot off missive after missive highlighting the comments, including putting Romney’s image on a proposed new $10,000 bill.

If it were an isolated case, it would be easier to ignore, but Romney has made a number of stumbles in that area. In Florida, he joked to a group of unemployed Floridians that he was “also unemployed,” and in August, it was revealed that he was planning to bulldoze his 3,009-square-foot beachfront house in California to make room for a new 11,062-square-foot pad.

Democrats, of course, have reliably played the class-warfare card, but Romney’s comments and overall aristocratic mien make him particularly vulnerable to these attacks.

With the economy still stagnant and a thin record by anyone’s standards, Obama’s reelection campaign will focus relentlessly on attacking the GOP nominee instead of running on accomplishments.

Indeed, an Obama strategist told GQ magazine this week that “in a reelect, all you’re really doing is trying to destroy the other guy.”

And with each passing week, it seems Romney is becoming more and more susceptible to destruction.

Heinze, the founder of GOP12.com, is a staff member at The Hill.