Former Gov. Ed Rendell, D-Penn., argued that presumptive Democratic nominee Hillary Clinton should not pick progressive star Sen. Elizabeth Warren, D-Mass., as her vice presidential candidate.

"I think Elizabeth Warren is a wonderful, bright, passionate person, but with no experience in foreign affairs and not in any way, shape, or form ready to be commander-in-chief," Rendell told a Philadelphia radio station, as Buzzfeed noted.

Warren is one of the most popular liberals in the country, so choosing her would ease Clinton's effort to unite the Democratic Party following the often acrimonious primary battle with Vermont Sen. Bernie Sanders. Senate Majority Leader Harry Reid, D-Nev., reportedly wants Clinton to pick Warren in part to avoid the possibility that she undermines Democratic efforts to retake the upper chamber by choosing a senator from a more competitive state.

Rendell's remark is a reversal from a little over a month ago, when he suggested that picking Warren might be a good idea.

"It would be, probably, against the conventional wisdom, but you remember when Bill Clinton tapped Al Gore people said [a] fairly young senator and governor from two southern states that border each other?" he said in April. "That's ridiculous. How can you do that? There's no diversity. There's no difference between the two of them. It's a bad ticket. It turned out to be a very powerful ticket and really catch the national imagination."

Still, Rendell noted that he is "not an insider in the campaign," and added that he offering the insight based on his personal relationship with Clinton. "I think she will not pick somebody that she feels in her heart isn't ready to be president or commander-in-chief," the former Democratic National Committee chairman said during Wednesday's interview.

The interview ended shortly thereafter, but Rendell called back to ensure he didn't give offense to Warren. "Elizabeth Warren's problem would be the same problem I'd have," he said in the follow-up. "I have no experience militarily, no experience in foreign affairs, and would be a difficult choice because if anything happened in week one and I became president, I would be lost."

In May, Rendell apologized for suggesting that Donald Trump had driven "ugly women" into the arms of the Democratic party. "Will he have some appeal to working-class Dems in Levittown or Bristol? Sure," Rendell said. "For every one he'll lose, one-and-a-half, two Republican women. Trump's comments like, 'You can't be a 10 if you're flat-chested,' that'll come back to haunt him. There are probably more ugly women in America than attractive women. People take that stuff personally."