Kentucky Sen. Rand Paul  and Arizona Sen. John McCain are once again banging heads – this time over whether to arm Syrian rebels – in the latest dispute that underscores a divide in the GOP and intensifies the fight over what the party will represent in 2016 and beyond.

Paul, a first-term senator and Tea Party favorite surging in popularity, took the latest shot by opposing aid to the rebels – a key part of McCain’s plan to end the two-year Syrian civil war in which 70,000 civilians and others have been killed.

“It is very clear that any attempt to aid the Syrian rebels would be complicated and dangerous, precisely because we don’t know who these people are,” Paul wrote in an opinion piece earlier this week. “The situation in Syria is certainly dire. … Al Qaeda is making confirmed inroads into the country. No one wants to see Syria become a bastion of extremism. But like other American interventions in the past, U.S. involvement could actually help the extremists.”

But McCain, fresh off a secret trip to Syria, on Friday upped his call for intervention — telling the Associated Press the opposition needs heavy weapons.

McCain and Paul split last month as members of the Senate Foreign Relations Committee when McCain, elected to Congress in 1983, voted in favor of the Syria Transition Act, which calls for “limited lethal and non-lethal assistance and training to vetted Syrian groups.”

Paul voted against the bill and warned in his op-ed Thursday for CNN that the U.S. now “has reason to believe” that Libyan rebels who helped overthrow dictator Moammar Gadhafi and whom McCain appeared to supported in 2011 were in fact connected to al Qaeda and other Islamic extremists. The bill passed by a 13-5 vote.

Their ideological fight is just one of several among Republicans as members seek to define and reshape the party after losing the last two presidential elections.

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