President Obama's pitch for congressional approval to attack Syria is getting a boost from some unusual allies: Republican leaders on Capitol Hill.

House Speaker John Boehner (R-Ohio) said Tuesday that he would support Obama's call for a strike against Syrian President Bashar al-Assad's government, in retaliation for Assad allegedly using chemical weapons against Syrian civilians. "This is something that the United States, as a country, needs to do," Boehner said.

Boehner was quickly joined by House Majority Leader Eric Cantor (R-Va.), who has famously undercut his boss in the past. The expression of support from the House came a day after Sen. John McCain (R-Ariz.) gave Obama his tentative backing, saying that if Obama's plan is defeated by Congress it would be "catastrophic" for America's international credibility.

The support of Boehner and Cantor could spell the difference between victory and defeat in the GOP-controlled House. As Brett LoGiurato notes at Business Insider, "They rarely get out publicly ahead of [Boehner's] Republican conference, so it suggests that they feel strongly about the issue," and "will be crucial, active voices in getting other House Republicans to support the authorization of military force."

However, Boehner is not exactly the most powerful speaker the U.S. Congress has ever seen. Feisty members of his caucus have left him high and dry on numerous occasions, on issues ranging from food stamps to taxes on millionaires.

There is also no denying that rallying conservative support for anything Obama wants to do is a tough sell. Indeed, much of the GOP opposition "is rooted in nothing more than the identity of the president who proposed it," says Greg Sargent at The Washington Post.

Then there is the growing split between the party's hawks and anti-interventionists, led by Sens. Rand Paul (R-Ky.) and Ted Cruz (R-Texas), both Tea Party favorites. "[E]ven Republicans who are not active supporters of Mr. Paul recognize that the country and their party are susceptible to a come-home-America message at a moment of war weariness and, among conservatives, profound distrust toward Mr. Obama," says Jonathan Martin at The New York Times.

There is concern, too, among Republicans that U.S. involvement could end up helping Syrian opposition groups associated with al Qaeda. "Many Republicans will never be convinced the U.S. can come to the aid of good rebels in Syria without also helping bad rebels in Syria," says Byron York at the Washington Examiner. "It's just too complicated, they believe, and there are simply too many bad guys. Why risk aiding al Qaeda or its affiliates?"

Still, every bit of cover from GOP leaders will increase the chance that the internal battle between Republican interventionists and isolationists will tip in the favor of Obama. Jennifer Rubin says at The Washington Post that the question is bigger than partisan politics. "If we ever attempt to adopt the Paul/Cruz worldview, we would soon find we've compromised our humanity and our security," she says. "Every 'ally' (and what reason would they have to remain our ally?) would be a sitting duck."

Ultimately, Republicans might be swayed by another factor: Their desire to keep all options open when it comes to going after one of Syria's main allies, Iran. As Ed Kilgore notes at Washington Monthly, the main foreign policy objective unifying Republicans for years has been "a desire for military action against Iran." Preserving that hope might be a bigger incentive than anything Boehner may or may not say.