Sen. John McCain (R-Ariz.) (AP Photo/J. Scott Applewhite)

The new head of the anti-tax Club for Growth said Tuesday his group may try to unseat Sen. John McCain (R-Ariz.) in 2016 by backing a Republican primary challenger against him.

McCain's response: Bring it on.

"In Arizona, we will watch that carefully," Club for Growth President David McIntosh told reporters at a Christian Science Monitor breakfast. He said the group, which has made a habit of taking on Republican incumbents in recent elections, will monitor the contest to see whether conservative Reps. David Schweikert or Matt Salmon enter the race.

"We'll do research, including polling, and determine: Is there a path to victory and is the money well-spent?" he explained.

McCain has an 83 percent lifetime rating, according to the Club for Growth's 2013 scorecard.

"They are free to do exactly what they decide," said McCain, when asked by The Washington Post about McIntosh's comments. "My only point, I guess, is that I'll be glad to match my record up against anybody's as far as growth is concerned."

McCain said last fall that he is "leaning toward" running in 2016, but has not made a final decision. He said the threat of the Club for Growth spending money against him isn't a factor in his decision-making process.

"It doesn't affect me in the slightest, I promise you," he said.

McIntosh recently took over for Chris Chocola as head of the Club for Growth. Like Chocola, McIntosh is a former Indiana congressman.

He said his group is unlikely to endorse a candidate in the Republican presidential primary, if history is an indication. But speaking for himself, McIntosh praised Indiana Gov. Mike Pence, a potential White House hopeful.

"I would be very excited" if Pence runs, McIntosh said.

The Club for Growth has endorsed a handful of Republican senators facing reelection, most of whom were elected in the 2010 tea party wave: Marco Rubio of Florida, Rand Paul of Kentucky, Pat Toomey of Pennsylvania, Tim Scott of South Carolina, Mike Lee of Utah and Ron Johnson of Wisconsin.

The organization has butted heads with the Republican establishment in recent years for spending heaps of cash to unseat Republican incumbents. It took heavy criticism for backing Richard Mourdock in 2012. Mourdock defeated then-Sen. Richard Lugar (Ind.) in the Republican primary. But he lost in the general election after a disastrous campaign in which he made controversial comments about rape and pregnancy.

"I think even when life begins in that horrible situation of rape, that it is something that God intended to happen," said Mourdock.

McIntosh said Club for Growth members have not yet overwhelmingly decided which Republican senator they want to take on in a primary this election cycle.

"I think at this point, people are waiting to see what happens in these races," he said.

McIntosh expressed a desire to unseat Senate Minority Leader Harry M. Reid (D-Nev.). But he voiced concerns about Gov. Brian Sandoval's (R) record. Sandoval is regarded by most Republican strategists to be the strongest possible challenger against Reid.

"Because of his record raising taxes, he's somebody the club would not engage in supporting," said McIntosh.