Brian Snyder / Reuters Republican presidential candidate Mitt Romney speaks at a campaign rally at the Military Aviation Museum in Virginia Beach on Sept. 8, 2012

Every campaign starts with a theory of the case. In 2004, George W. Bush’s advisers surmised a shaken country wanted a leader who had the strength to take tough decisions to keep us safe. Four years ago, Barack Obama ran on change and against George W. Bush. On the day he entered the race 15 months ago, the organizing principle of Mitt Romney’s campaign was that the 2012 election would hinge on Obama’s mishandling of the sluggish economy. Romney is still promoting the case that he has the job-creating chops the President lacks. But as Election Day nears, he has begun to build a new, aggressive campaign atop the foundation of his old one.

Appearing on Meet the Press this weekend for the first time this cycle, Romney was asked by David Gregory to write his campaign’s bumper sticker. “It’s basically–you want more jobs, you want higher income? Then vote for Romney and Ryan,” he said. This was vintage Romney: the candidate who aspired to center-right acceptability, citing the bipartisan accomplishment of his governorship, praising elements of Obama’s health care reform, and stressing above all the health of the economy.

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A different Mitt Romney showed up in Ohio on Monday. This was the flame-throwing, base-juicing nominee of an increasingly conservative party, the guy who frequents NASCAR events, rallies with hard-right icons and raps his opponent for remaking America as a godless European nanny state. Addressing supporters at a metal fabricator in Mansfield, Romney attacked Obama for the rise in food stamp recipients and his role in crafting impending cuts to the defense budget. Earlier Monday, he weighed in on the Chicago teachers’ strike, using a local spat in a city he claims to disdain to swipe at unions and hem in Obama between his former chief of staff and a key Democratic constituency. At rallies over the weekend in the conservative strongholds of Western Iowa and Virginia Beach, Romney appeared alongside Congressman Steve King — who edges so far right he makes Todd Akin look like Barney Frank — and controversial televangelist Pat Robertson, and laced his stump speech with unbidden affirmations of his love for God and country.

It’s not that Romney has abandoned his focus on the economy as the paramount issue of the campaign. But over the past few months, both in television ads and remarks to partisan audiences, the cool emphasis on his Mr. Fix-It business credentials have increasingly jockeyed for space with hot-button, base-mobilizing rhetoric.

Since the summer, when an Obama ad onslaught casting Romney as a heartless moneybags began opening the incumbent’s narrow lead in the polls, Romney has been letting the red meat fly. In Michigan, he cracked a birther joke. In Virginia, he intimated Obama wanted to “take God off our coins.” His campaign cut a TV spot falsely accusing Obama of gutting welfare reform, then scoffed at fact-checkers’ outrage and anointed it “our most effective ad.”

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Why has Romney veered from the economic script his advisers still say is enough to win the presidency? The answer is simple: the argument wasn’t enough. In a year when swing voters are a vanishing breed, tailoring a message for the political center is still sensible, but not sufficient. The first major sign that Romney recognized this was his selection Paul Ryan as his running mate, and his subsequent embrace of the Wisconsinite’s austere budget. Picking Ryan was a chancy move for a candidate averse to risk. It was a base play. And while it afforded Romney a new identity — that of the conservative reformer ready to make tough choices, rather than the expedient tactician — it also likely betrayed a recognition that absent a shakeup, the Republican was on course to lose. Why else would he abandon the frame that the election was a referendum on Obama, and instead cast it as a choice on an issue (Medicare) on which Democrats have historically dominated?

But Ryan hasn’t been responsible for Romney’s falling poll numbers. (A CNN/ORC poll released Monday showed Obama up six points nationally, 52%-46%, in the wake of a strong convention.) Rather, the culprit is his inability to coax voters into assigning Obama a larger share of the blame for the dismal economic recovery.

Romney advisers still profess confidence. “The reality of the Obama economy will reassert itself as the ultimate downfall of the Obama Presidency, and Mitt Romney will win this race,” Romney pollster Neil Newhouse argued in a memo released Monday, on the heels of a raft of surveys showing the kind of post-convention bump for the incumbent that Romney failed to earn. But in August, a senior Romney aide also predicted a post-convention bounce for the challenger of up to 11 points. And in the new CNN poll, Obama has managed, remarkably, to open a one-point lead on the question of who would better handle the economy. Yes, it’s a virtual tie taken at a moment when polls tend to be most volatile — but it also underscores the weakness of Romney’s original case against the President. By a two-to-one margin, according to one poll this summer, voters still blame Obama’s predecessor for the dismal economy.

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Which may explain why Romney is running two campaigns. On the national stage, when undecided voters are tuning in, he is the sensible private-sector executive eager to cross the aisle to get America working again. His surrogates gently tell frustrated voters that the Obama’s not a bad guy — just a bad President. The ads geared toward this centrist audience are designed to assuage guilt: “He tried. You tried. It’s OK to make a change,” says one. And then there’s the other Mitt Romney, the one who fires up partisan crowds on the campaign trail, who frets about creeping secularism and blasts Obama for running a campaign of “anger and hatred.”

The split-screen messaging is not unusual; all candidates tailor their message to their audience. But it is a sign that the Romney brain trust realizes that their original game plan isn’t panning out as they drew it up.

Cover Story: The Mind Of Mitt