Douglas Graham/Roll Call/Getty Images Lindsey Graham knows a little something about Hillary Clinton's abilities. Back in 2003, the two Senate colleagues appeared together to talk about health care for National Guard and Reserve members.

WASHINGTON -- Sen. Lindsey Graham (R-S.C.) still isn't sure which candidate he'll back in the GOP primary for president, but it won't be Sen. Ted Cruz (R-Texas).

"Ted's smart, but I think that Hillary Clinton would do a number on him," Graham told Fox News radio host Brian Kilmeade on Friday.

Graham, who dropped his own presidential bid late last month, has said that challenging Cruz -- as well as Sen. Rand Paul (R-Ky.) -- was one of the main reasons he launched his campaign in the first place. He has called Cruz an extremist for being willing to shut down the federal government, and he has criticized Cruz's foreign policy approach.

Last month, Graham said that by opposing U.S. involvement early on in the Syrian crisis, the Texas senator "has done more to allow ISIL to gain a foothold in Syria than any senator other than Rand Paul."

"Frankly, he isn't ready for the job. His foreign policy is very uneven," Graham said of Cruz on Friday.

The South Carolina senator did have praise for some of his other former competitors, including Florida Sen. Marco Rubio (he has a "terrific foreign policy"), Ohio Gov. John Kasich, New Jersey Gov. Chris Christie, former Hewlett-Packard CEO Carly Fiorina and former Florida Gov. Jeb Bush.

"I like Jeb a lot," he said, adding that he feels close to the Bush family. "Don't write Jeb Bush off."

Graham clarified, however, that he isn't ready to endorse Bush or anyone else quite yet.

Asked about front-runner Donald Trump, Graham said he believes the real estate mogul is "coachable" on foreign policy.

Graham has said in the past that he wouldn't rule out accepting a Cabinet position in a potential Trump administration.

Also on HuffPost:

PHOTO GALLERY Sen. Ted Cruz