Remember Rosie Ruiz? In 1980 she was the first woman to cross the finish line at the Boston Marathon – except it turned out that she hadn't actually run most of the race, that she sneaked onto the course around a mile from the end. Ever since, she has symbolized a particular kind of fraud, in which people claim credit for achieving things they have not, in fact, achieved.

And these days Paul Ryan is the Rosie Ruiz of American politics.

This would have been an apt comparison even before the curious story of Ryan's own marathon came to light. Still, that's quite a story, so let's talk about it first.

It started when Hugh Hewitt, a right-wing talk-radio host, interviewed Ryan. In that interview, the vice-presidential candidate boasted about his fitness, declaring that he had once run a marathon in less than three hours.

This claim piqued the interest of Runner's World magazine, which noted that marathon times are recorded – and that it was unable to find any evidence of Ryan's accomplishment. It eventually transpired that Ryan had indeed once run a marathon, but that his time was actually more than four hours.

In a statement issued by a spokesman, Ryan tried to laugh the whole thing off as a simple error. But serious runners find that implausible: The difference between sub-three and over-four is the difference between extraordinary and perfectly ordinary, and it's not something a runner could get wrong, unless he's a fabulist who imagines his own reality. And does suggesting that Ryan is delusional rather than dishonest actually make the situation any better? Which brings us back to the real issues of this presidential campaign.

Obviously nobody cares how fast Ryan can run, and even his strange marathon misstatement wouldn't be worth talking about in isolation. What makes this incident so striking is, instead, the way it resonates with the essential Rosie-Ruizness of Ryan's whole political persona, which is built around big boasts about accomplishments he hasn't accomplished.

For Ryan, as you may recall, has positioned himself as an icon of truth-telling and fiscal responsibility, while offering policy proposals that are neither honest nor responsible. He calls for huge tax cuts, while proposing specific spending cuts that, while inflicting immense hardship on our most vulnerable citizens, would fall far short of making up for the revenue loss. His claims to reduce the deficit therefore rely on assertions that he would make up for the lost revenue by closing loopholes that he refuses to specify, and achieve further huge spending cuts in ways that he also refuses to specify.

But didn't the Congressional Budget Office evaluate Ryan's plan and conclude that it would indeed reduce the deficit? I'm glad you asked that. You see, the budget office didn't actually evaluate his plan, because there weren't enough details.

Instead, it let Ryan specify paths for future spending and revenue, while noting – in what sounds to me like a hint of snark – that "No proposals were specified that would generate that path." So Ryan basically told the budget office to assume that his plan would slash the deficit, then claimed the resulting report as vindication of his deficit-slashing claims. Sorry, but that's the policy equivalent of sneaking into a marathon near the finish line, then claiming victory.

Still, Mitt Romney, not Ryan, is the presidential candidate, although that's sometimes hard to remember. So how does Romney/Ryan differ from Ryan alone? It's worse. Like the Ryan plan, the Romney plan offers huge tax breaks to corporations and the wealthy, while pledging to offset these cuts by closing unspecified loopholes; but Romney adds to the implausibility by also demanding higher defense spending and eliminating the Medicare cost savings contained in Obamacare. Realistically, the Romney plan would explode the deficit, not reduce it.

Yet Romney boasts about his fiscal responsibility; in Tampa he accused President Barack Obama of hurting the economy with big deficits (while also declaring that Obama was destroying jobs by cutting military spending – go figure), then declared that "We will cut the deficit and put America on track to a balanced budget." Yep, he's another Rosie Ruiz Republican.

So what is this election about? To be sure, it's about different visions of society – about Medicare vs. Vouchercare, about preserving the safety net vs. destroying it. But it's also a test of how far politicians can bend the truth. This is surely the first time one of our major parties has run a campaign so completely fraudulent, making claims so at odds with the reality of its policy proposals.

But if the Romney/Ryan ticket wins, it won't be the last.

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