WASHINGTON — The Congressional vote on whether to strike Syria will offer the best insight yet on which wing of the Republican Party — the traditional hawks, or a growing bloc of noninterventionists — has the advantage in the fierce internal debates over foreign policy that have been taking place all year.

Republican divisions on national security have flared over the use of drones, aid to Egypt and the surveillance practices of the National Security Agency, and the tensions have played out publicly in battles between Senator John McCain of Arizona, a former Navy pilot and Vietnam prisoner of war, and Senator Rand Paul of Kentucky, a libertarian-leaning freshman. Mr. McCain memorably called Mr. Paul and his compatriots “wacko birds,” and Mr. Paul suggested that hawks like Mr. McCain were “moss covered.”

But those intermittent spats could pale in comparison with the fight over whether to attack Syria, an issue on which Mr. McCain, a former Republican presidential candidate, and Mr. Paul, a possible contender in 2016, will almost certainly be the leading spokesmen for their party’s two wings.

Mr. McCain has long advocated intervention in Syria’s civil war. After meeting with President Obama at the White House on Monday, he said that it would be “catastrophic” if Congress did not approve the president’s proposal and that such a rejection would result in the United States’s credibility being “shredded.”