Indeed, Syria has tilted the political landscape 90 degrees, turning the familiar partisan divide into a vertical split between the leadership in both parties, which favors military intervention, and the parties’ anti-interventionist grassroots bases. And it comes on the heels of a revival of “libertarian populism” on the right, alarm over civil liberties on the left, and a general war weariness among Americans of all stripes.

The Tea Party has been nearly unanimous in its opposition to strikes against Syria, and Matt Kibbe, president and CEO of FreedomWorks, a Tea Party group, thinks it’s more than just knee-jerk opposition to Obama. “It’s a shift; it’s a realignment,” Kibbe said. On issues such as civil liberties, electronic surveillance, drones, and criminal-justice reform, “there’s absolutely a convergence. We’re building a new coalition.”

“You’re seeing coming to fruition a lot of the groundwork that was laid over several years,” Miles said. It started in Iraq, with antiwar House Republicans such as Paul and North Carolina’s Walter Jones, he said, and has materialized more recently in bipartisan legislation to trim defense spending.

One lawmaker who has tapped into that coalition is freshman Rep. Thomas Massie of Kentucky, a Republican who has introduced bills with Democrats to legalize industrial hemp production and end mandatory minimum sentences. He told National Journal that the grassroots opposition to Syria was unlike anything he’s seen since the populist furor over the bank bailouts in 2009. And it may be just the tip of the iceberg. “It’s certainly not a one-off,” Massie said. “I think there are a lot of opportunities going forward.”

If you want a glimpse of what this coalition might look like, the July roll-call vote on the amendment to end National Security Agency bulk surveillance sponsored by Reps. Justin Amash, R-Mich., and John Conyers, D-Mich., is a good place to start. The measure earned 111 Democratic and 94 Republicans ayes and split the parties internally between more-hawkish leaders and the privacy-minded rank and file. The Washington Post’s Greg Sargent compared the result to a whip count on Syria and found “striking” overlap.

The two sides often come to the same issue for completely different reasons. The National Rifle Association, for instance, recently joined the American Civil Liberties Union on a lawsuit challenging the NSA’s surveillance programs. The NRA’s concern is that surveillance could be used to create a national gun registry -- a fear that critics dismiss as conspiratorial -- but whatever the motive, the ACLU is happy for the support.

But while a constituency might be there, no movement now exists to channel the energy bubbling up from the grassroots into real political power. Instead, the populist wings of the left and the right tend to organize themselves in parallel and have little interest in joining forces -- at least publicly. “When it comes to grassroots organizing, you see different groups coming together on certain votes,” Kibbe said, “then going back to their respective camps when it comes time for politics.”