Sept. 5, 2012 -- Having spent the last 14 years in Congress building a political brand rooted in his avowed devotion to telling "hard truths," Republican vice presidential nominee Paul Ryan entered this election season as no one's favorite to be accused of habitual dishonesty on the campaign trail.

The Wisconsin congressman's positions on debt and deficit reduction have never been about political posturing, supporters say. Rather, they are the logical result of years spent mining the numbers, just a man and his calculator, making dire calculations about the country's fiscal path.

And yet, less than four weeks since being introduced as Mitt Romney's running mate, Ryan has given rise to a furious fact-check revolution, with analysts warning his claims -- about everything from Health Care reform to his best marathon time -- could imperil what many had painted as his cardinal virtue: Honesty.

It's a stark departure from just two months ago, when The New Yorker's Ryan Lizza called Ryan the leader of the Republican party's "attack and propose faction," an ideas man (and counterpoint to some of his obstructionist Republican colleagues) who had written and passed budgets in the House and drafted two versions of his fiscal manifesto, "The Roadmap."

"The Roadmap" is Ryan's defining document, and modern conservatives' most pointed and detailed explanation of how they would go about settling America's debts. It calls for cuts to everything -- taxes, entitlement programs, they all get slashed. And then, according to the plan, after about 50 years -- sometime in the 2060s -- the government begins to break even.

"Ryan has, up to this point, been viewed and as an ideologue, but one with whom you could have a fair disagreement," Larry Parnell, the director of The George Washington University Strategic PR Master's program, told ABC News. "He has the reputation of being straightforward, consistent, and articulate."

But signing on as the No. 2 to any presidential ticket comes with built-in risk. Ryan, Parnell said, has had to dial back his hawkish positions on spending, Medicare reform, and abortion to avoid clashing with Mitt Romney's more centrist platform.

"[Ryan] can't go back to being the guy he was before." Parnell said. "He had to become something else [to fit in], and he's embraced it."

"I think what this does is create a reputation as Ryan not being terribly different than how the public perceives any other politician," Geoffrey D. Peterson, the director of the University of Wisconsin-Eau Claire's Political Research Institute, told ABC News. "So, I think it would make it more difficult for Ryan to portray himself as 'the last honest man in Washington' in the future than he might have been able to six weeks ago."

Most of the critical focus has been directed toward Ryan's speech at the Republican National Convention in Tampa last week.

It was there, before a naturally partisan and obviously delighted audience, that he claimed President Obama had "funneled" $716 billion from Medicare to pay for the new health care law, ignoring the fact that his own "Roadmap" had called for the same savings, accrued in the same manner: By capping reimbursements to medical providers, not beneficiaries.

Ryan also blamed the president's economic policies for Standard & Poor's Aug. 5, 2011, decision to cut the long-term U.S. credit rating. But S&P's initial explanation disputes that, blaming the summer's debt-ceiling brinksmanship -- which took place mostly in Congress, with Ryan playing a vocal role -- and the resulting economic uncertainty for driving their decision.

In his convention speech, Ryan claimed that President Obama, when confronted with the Simpson-Bowles deficit reduction committee's "urgent report," "thanked them, sent them on their way, and then did absolutely nothing." But Ryan omitted a crucial point: The Simpson-Bowles recommendations never made it to the Senate because a seven-member panel, with Ryan leading the way, voted against sending them there.

Asked by Matt Lauer on the "Today" show Tuesday if he "owed it to people [at the Republican convention] to say that as well," Ryan demurred, pointing instead to an "alternative" measure he submitted in the House, which passed on party lines and were ignored by the Senate.

But even as the fact-checkers piled on after Ryan's speech, the candidate seemed unfazed. Speaking to "Good Morning America's" George Stephanopoulos Tuesday, he showed no signs of backing off his Medicare claims.

"If you're taking $716 billion from Medicare to finance Obamacare, that really is a raid of Medicare for Obamacare," he said. "Our plan to save Medicare does not affect or change the benefits for anybody who is in or near retirement."

He'd repeat the claim on a third morning show, just minutes later.