(AP) President Barack Obama's proposal to bomb Syria is dividing both political parties as they cope with Iraq war weariness and, in the GOP, the rise of libertarian sentiment. The dilemma is most acute, however, for Senate Republican leaders who already were worried about tea party-backed challengers to their re-election bids back home.
Unlike his House counterparts, Senate Republican leader Mitch McConnell took no clear stand on the matter Tuesday. For now, he's letting rank-and-file colleagues debate whether to approve the proposal to fire missiles at Syrian government targets, Congress' biggest foreign policy decision in years.
McConnell, one of Washington's longest-serving and best-known Republicans, faces a challenger from the right in Kentucky's GOP Senate primary next year. Complicating matters is his fellow senator in the state. It's Rand Paul, a tea party hero and leader of noninterventionist lawmakers who say attacking Syria is not in the United States' interest.
Paul, who may follow his libertarian-leaning father in running for president, defeated McConnell's choice for Senate in 2010. Ever since, McConnell has worked hard to court Paul and his supporters, sometimes sitting on the sidelines while other Senate Republicans hammered out difficult compromises on matters such as immigration.
McConnell's caution on Syria contrasts with the support Obama received Tuesday from the House's Republican leaders. After meeting with Obama at the White House, Speaker John Boehner, R-Ohio, said, "I'm going to support the president's call for action." He suggested his colleagues do the same.
The House's second-ranking Republican, Majority Leader Eric Cantor of Virginia, was equally clear. "America has a compelling national security interest to prevent and respond to the use of weapons of mass destruction, especially by a terrorist state such as Syria," Cantor said.
McConnell attended the same White House meeting. But he quickly left for Kentucky, while numerous senators attended a closed briefing on Syria and the Senate Foreign Relations Committee conducted an open hearing.
McConnell thanked Obama and said in a statement, "Congress and our constituents would all benefit from knowing more about what it is he thinks needs to be done and can be accomplished in Syria and the region."
The Senate's second-ranking GOP leader, John Cornyn of Texas, also proceeded cautiously. Obama "needs to explain in detail what vital national interests are at stake, his plan for securing these interests and a clear definition of what success looks like in Syria," Cornyn said in a statement. Like McConnell, he faces re-election next year in a state where a tea party champion beat an establishment Republican in the last Senate race.
The House's and Senate's top Democratic leaders, meanwhile, have endorsed Obama's call for military action against Syria's government, accused of using chemicals to kill hundreds of civilians in rebel areas.
The Syria question is dividing Republicans in ways that domestic issues rarely do. GOP lawmakers, for instance, are virtually unanimous in opposing new taxes even on the wealthiest Americans in times of large budget deficits, and even if Democrats agree to big spending cuts in return.
The recent elections of Paul and other libertarian-tinged conservatives highlight a growing Republican willingness to challenge traditional military hawks and interventionists such as Sen. John McCain, R-Ariz. Disillusionment over the Iraq and Afghanistan wars cuts across many political lines, creating odd left-right alliances that don't exist elsewhere. 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. Many Republican lawmakers still support a strong U.S. military presence worldwide, he said, but "the noninterventionists are more vocal" in recent years.
McConnell hasn't always been quiet about international matters. He was a leading critic of the military dictatorship in Myanmar, or Burma. He once chaired the Appropriations subcommittee responsible for the State Department's budget.
With his 2014 re-election campaign underway, McConnell has seemed less hawkish at times. Earlier this year, he joined 12 other Republicans in voting to cut off U.S. aid to Egypt. Israel opposed the move, but tea party Republicans such as Paul and Ted Cruz of Texas pushed it nonetheless.
Such votes haven't appeased Matt Bevin, the tea party-affiliated Kentucky businessman trying to oust McConnell in the Republican Senate primary. Bevin strongly opposes intervention in Syria and accuses McConnell of being a wishy-washy conservative across the board.
"It's a very difficult position for McConnell to be in," said Dan Schnur, a former top Republican adviser who teaches political science at the University of Southern California.
Schnur said Boehner is taking some risks by backing Obama on Syria when many House Republicans have expressed strong reservations.
Boehner "knows that Republicans don't benefit from becoming the isolationist party," Schnur said. Rejecting Obama's Syria resolution, he said, would "take the Republicans back to a pre-Reagan, pre-Nixon, pre-Eisenhower approach to foreign policy."
Some tea partyers and libertarian-leaning Republicans say it's time for that change. Republicans in Chesterfield County, S.C., recently censured Sen. Lindsey Graham, R-S.C., for his strong support of U.S. military action against Syria.
Debbie Dooley, national coordinator for Tea Party Patriots, said she supports an active U.S. presence military abroad, including acts of war, "when a clear American interest is involved." But engaging in Syria "is completely ridiculous," Dooley said, because the civil war factions on both sides "want to destroy us."
Holt, who has advised several Republican campaigns, said mixing local political concerns with national security needs "is always a bad thing." He said McConnell's statement Tuesday leaves ample room for eventually backing an attack on Syria.
McConnell "is being more cautious," Holt said, "and reflecting, 'Why should I support a president who hasn't shown more resolve on the international stage?'"
Holt, generally seen as an establishment Republican, said his party's members "are going to have to overlook their distrust of Obama to do the right thing."
Associated Press writer Bill Barrow in Atlanta contributed to this report.