President Obama's call for Congress to authorize a limited attack against Syria has scrambled the traditional partisan divisions on Capitol Hill.

Republican politicians who only weeks ago were urging Obama to intervene — such as former vice presidential candidate Rep. Paul Ryan (Wisc.) and Sen. Marco Rubio (Fla.) — suddenly have their doubts. Indeed, unlike the preludes to most of the U.S.'s military actions in the last few decades, the stiffest opposition is coming from Republicans, rather than Democrats.

There's a good chance that an attack on Syria could founder on the rocks of the GOP-led House, where "80 percent of the House Republican Conference is, to some degree, opposed to launching strikes in Syria," say Jonathan Allen and Jake Sherman at Politico. And if the GOP were to lead the anti-interventionist charge on the country's most important foreign policy decision in years, it very well could erase the strong national security platform that was once at the heart of the party's brand.

The "staggering shift" — as Fred Kaplan called it last year at Slate — was already well underway during the 2012 presidential campaign, when Democrats talked up President Obama's "backbone" and overseas successes, including the killing of Osama bin Laden, while his Republican rival, Mitt Romney, remained focused on the economy.

The transformation has only accelerated with the rise of Sens. Rand Paul (R-Ky.) and Ted Cruz (R-Texas), both of whom are very popular with the conservative base. They have carved out a formidable neo-isolationist wing within a party that was dominated by hawks and neo-conservatives only a few years ago.

The shift has also been reflected in lobbying by influential conservative think tanks like the Heritage Foundation, which opposes U.S. involvement in Syria. "It's pretty striking that Heritage has decided to go full libertarian under [Heritage Foundation President Jim] DeMint and abandon four decades of leading the Reagan 'peace-through-strength' caucus," one senior Republican aide tells National Journal.

Still, given the toll the wars in Afghanistan and Iraq have taken, perhaps we shouldn't be surprised. Here's Charles Babington at the Associated Press:

Disillusionment over the Iraq and Afghanistan wars cuts across many political lines, creating odd left-right alliances. Lawmakers on the left and right also note the military's heaving spending, which contributes to budget deficits.

"Both parties have become much more wary of exerting American force on the international scene," said longtime Republican consultant Terry Holt. [AP]

Another factor that will mitigate the impact of the Syria issue on the GOP's image is the fact that the public happens to agree with the doubters on this one. Andrew Stiles notes at National Review that nearly 60 percent of Americans, including 54 percent of Democrats, said in a Washington Post/ABC News poll that they oppose military action in Syria.

It remains unclear, however, whether the GOP's drift into isolationism will mark a permanent shift in the party's identity. Conservatives have justified their opposition to Obama's plan by saying they simply don't have faith in his leadership, or find his Syria policy incoherent. That suggests they are open to using force overseas, just not while Obama is commander-in-chief.

More cynical observers have suggested that the GOP's newfound opposition to military adventures overseas is purely political. "Republicans don’t like what Obama is doing in Syria — whatever it is," says Dana Milbank at The Washington Post.

Either way, the risks for the GOP remain. "If [Rand Paul] becomes the face of the GOP," says Jennifer Rubin at the Post, "Democrats will establish a monopoly on national security reliability they could only have dreamed of during the Reagan-Bush years."