On the surface, Mitt Romney’s selection of Paul Ryan as his vice-presidential running mate is both daring and smart. It’s daring, obviously, because Ryan’s budgetary vision of a drastically reduced federal government presents such an existential threat to liberalism that it may unite Democrats in a death-or-glory stand behind President Obama. But it’s smart because Ryan has been one of the only Republicans since Ronald Reagan capable of inspiring the right while reassuring moderates. Indeed, one of the refrains of Ryan's career has been his courtship of moderates within his party and outside of it. This is a strategy with a proud tradition in the modern Republican Party, hailing back to the landmark efforts of Ronald Reagan, Dwight Eisenhower, and William F. Buckley.

But if Ryan has been reasonably successful at that task until now, his effort will most likely soon come precipitously undone. Moderates around the country will be tempted to vote for the GOP this year, but as they are made to take a closer look at the radicalism of Ryan’s budget and of his intellectual influences, it's safe to say they won't like what they find. This is a reality that Ryan's affable personality simply won't be able to paper over. And so, rather than bolster the cause of conservatism, it's far more likely that Ryan’s selection will have the opposite effect—that of undermining the long-term viability of the Republican Party.

IN THE TRADITION of his mentor Jack Kemp, Ryan has long engaged in spirited dialogue with moderates, those colleagues and voters who are fiscally conservative though socially broad-minded. Unlike most of the other politicians who excite the conservative base, he comes across as modest, intelligent, thoughtful, well-informed, and temperamentally moderate. Though a religious Catholic, he has to this point shown little interest in divisive culture-war issues. Occasionally he has bucked the GOP line, as in 2007 when he was one of the few Republicans voting for a Democratic bill banning employment discrimination based on sexual orientation. While he is a favorite of RINO-hunting groups like the Club for Growth, he is a big-tent Republican who resists calls to purge GOP dissenters. According to Robert Draper’s recent book about the House, Do Not Ask What Good We Do, Ryan “hated squabbling amongst conservatives—the paleos versus the neos, the socials against the moderates… Ryan had long sought to be the GOP’s glue, pleading for adherence to the principles and the data.”

Like Ryan, moderates worry about unsustainable spending levels and metastasizing deficits, and agree that painful actions must be taken to reduce healthcare spending in particular. Ryan won the respect of many moderates by grappling with the numbers and producing concrete budget proposals, which passes as an act of breathtaking political courage in Washington these days. He has helped to counter the perception that Republicans are just negativists and obstructionists, bereft of ideas. Indeed, when Ryan grilled Treasury Secretary Timothy Geithner at a hearing in February, it was the Democrat who seemed out of ideas, admitting to Ryan that he didn’t have a “definitive solution” to the long-term problems of unfunded liabilities and rising deficits.

But the fact is that Ryan’s budgets are not moderate documents, and Ryan’s plan is not fiscally conservative but radical. Fiscal conservatism, if it means anything, requires that policymakers use both revenue increases and spending cuts to bring the budget into balance over the long term. By refusing to consider any tax increases at all, and in fact proposing to slash corporate and individual taxes by some $4 trillion above and beyond the Bush tax cuts, Ryan sides with those for whom fiscal policy is a matter of theology rather than economics. The fiscally conservative leaders from the GOP past, such as Dwight Eisenhower, would be appalled by the decades of deficits the Ryan plan envisions and puzzled by the apparent sacredness of the military budget; Ike cut military spending by 27 percent but Ryan would not reduce it by so much as a nickel.