WASHINGTON (CBS DC) — Sen. John McCain, R-Ariz., and potential 2016 presidential contender Sen. Lindsey Graham, R-S.C., teamed up against fellow GOP Sen. Rand Paul to label him “the worst possible candidate” for president, specifically because of his “isolationist” foreign policy.

McCain, who was the first Republican to run against President Barack Obama in 2008, responded to Paul’s accusation that he and Graham are both “lapdogs” for Obama’s similarly hawkish foreign policy, specifically noting Libya and Syria. Speaking with Fox News on Wednesday, McCain and Graham said that Paul’s selection as the GOP 2016 presidential nominee would destroy what they see as the central issue of the campaign: foreign policy.

“At the end of the day, his record, in my view, shows a foreign policy vision one step behind leading from behind,” Graham said during a briefing with reporters on Capitol Hill. “And all I can say is that if he’s the nominee, I will support him. But if he’s the nominee of the party, we risk giving up the central issue of the 2016 campaign, which will be foreign policy.”

“I think Senator Paul’s record on this issue is quite frankly behind that of President Obama,” added Graham. “[Paul has] the worst chance of anybody to make a case against Obama’s foreign policy.”

Paul had criticized the McCain, Graham partnership on Tuesday, telling Fox News that they’ve “been wrong about every foreign policy issue over the last two decades… I’m really the one standing up to President Obama, and these people are essentially the lapdogs for President Obama and I think they’re about that.”

McCain echoed a very similar foreign policy criticism as his fellow “lapdog” Graham, although the Arizona senator noted that an anonymous Obama administration official has referred to the duo as “Doberman Pinschers.”

“Senator Paul is the worst possible candidate of the 20 or so that are running on the most important issue, which is national security,” McCain told Fox News, saying that Paul doesn’t believe Iran is a threat to Israel, that he has doubted the strength of ISIS and proposed a defense budget cut in 2011. “The record is very clear that [Paul] does not have an understanding of the needs or the threats of United States national security.”

McCain, like Graham, said he would support the Republican Party’s nominee, but he thinks the “isolationist policies” will burn Paul in the GOP primary.

“I would support the nominee for my party, I am a loyal Republican. I would hope that good sense would prevail here, because the realities of the world today do not allow for isolationist policies,” said McCain. “We’ve already seen what happens from ‘leading from behind,’ leading from far behind, and that’s what Rand Paul would do, but I hope that many of us could prevail on him to see the world in a very different light.”

Asked again if he truly believes Paul is “the worst candidate” for president, McCain doubled down on the criticism.

“On national security? Absolutely. There is no doubt in my mind,” said McCain, noting his own choice for a 2016 presidential candidate: “Lindsey Graham. Lindsey Graham. First, last and always.”

— Benjamin Fearnow