Widely suspected of believing in nothing, Mitt Romney’s choice of a True Believer as his running mate plays well as public theater. As a TV performer, Wisconsin congressman Paul Ryan is as winsome as Sarah Palin, and far better at faking sincerity.

Although women are generally smarter about this kind of thing than men, Ryan’s puppy-dog eyes and altar boy demeanor make him a formidable campaigner. Had he not gone into politics, he’d have made a terrific Irish-Catholic funeral director. Not for nothing did his high school classmates in Janesville, Wis. elect him class president and, more tellingly, “Biggest Brown-Noser.”

Surely, this polite Midwestern family man couldn’t possibly be the heartless fanatic that Democrats portray. Maybe the most telling passage in Jonathan Chait’s prescient New York Magazine profile of Ryan was the author’s exchange with James B. Stewart, the legendarily inept New York Times business columnist.

(During the great “Whitewater” snipe hunt, Stewart once appeared on “Nightline” predicting Hillary Clinton’s imminent indictment for falsifying a loan application. It turned out that Stewart himself had neglected to examine the second page of a two-page document. You’d be laughed off the sports page for that, but Washington punditry has its own rules.)

So anyway, in pursuit of the sacred illusion of “bipartisanship,” Stewart had written that Ryan’s latest ballyhooed tax reform scheme — he churns them out like the Politburo — had the potential to heal the nation’s fiscal divide, raise greater revenue and increase fairness by treating capital gains as ordinary income.

It’s true that doing that might almost make Ryan’s numbers work, but also true that, alas, Stewart had simply imagined it.

In reality, Chait pointed out, Ryan proposes not raising, but eliminating capital gains taxes altogether — so that a multimillionaire like, say, Mitt Romney, whose income derives from investments rather than work, could end up paying no federal income taxes at all. An enduring solicitude for the sufferings of plutocrats is the pole star of Ryan’s public life.

Stewart, however, suggested to Chait that Ryan couldn’t possibly be so cynical. He must have been “boxed-in” by right-wingers. He alibied that the Wisconsin congressman “seems very straightforward … He doesn’t seem cunning. He seems very genuine.”

Have I mentioned that Rep. Ryan is a very handsome fellow, with earnest puppy-dog eyes? Seeming guileless is his singular political talent. That, and a wholly undeserved reputation for intellectual seriousness and lack of personal ambition belied by his rapid rise to power.

It’s a great act. So what if it’s utterly fraudulent?

“America’s neighborhood accountant,” Time has called him, “a man devoted to the task of restoring our fiscal health.”

So would it shock you to learn that “America’s Accountant” was a total party line guy throughout the Bush administration? As a fiscal conservative, he recently confided to the New Yorker’s Ryan Lizza, “He was miserable during the last majority.” Not miserable enough to cast a single dissenting vote, however. History records that Ryan voted 100 percent of the time for Bush administration taxing and spending policies he now decries.

Ryan supported the Bush tax cuts of 2001 and 2003. He voted repeatedly for the unfunded wars in Iraq and Afghanistan. He backed the unfunded expansion of Medicare, Part D — with its huge profits for the pharmaceutical and insurance industries. He voted for the TARP bank bailouts, and for the Obama administration’s bailout of the auto industry, too.

Social Security privatization was also his baby. Had it been up to Ryan, the national debt would be a few trillion dollars higher. He pushed a plan even more reckless than President Bush’s, encouraging workers to plunge 50 percent of their payroll taxes into the stock market, while paying current beneficiaries through — you guessed it — deficit spending.

No telling where we’d be today had this scheme become law.

In short, it wasn’t Ryan’s principles that turned Janesville’s “Biggest Brown-Noser” into “America’s Accountant.” It was President Obama’s election. In the midst of the worst economic crisis since the 1930s, it wasn’t joblessness that worried him, it was government spending.

Ryan’s successive “Roadmaps for America’s Future” and “Pathways to Prosperity” — I believe we’re up to three manifestos now — share two traits: extreme intellectual dishonesty and arithmetic the distinguished gentleman appears to have pulled entirely out of his wazoo. That’s part of what Newt Gingrich meant when he called the Ryan budget “right-wing social engineering.”

The part that induced conservative columnist Charles Krauthammer to call Ryan’s latest budget proposal “the most annotated suicide note in history” is something Democratic strategists have actually had trouble getting voters to believe. Informed that Mitt Romney supported converting Medicare to a voucher plan, slashing Medicaid, while giving sweeping tax cuts to multimillionaires, focus groups responded with skepticism. Surely no politician would be that heartless and stupid.

For all his boyish charm, however, now that Rep. Ryan’s on the GOP ticket, the awful truth will be harder to hide.

(Gene Lyons can be reached by email Lyons at eugenelyons2@yahoo.com)