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President Barack Obama said today that Republican nominee Donald Trump “keeps proving” that he’s not fit for the Oval Office. The latest indicator of Trump’s temperament issues? His continued attacks on Khizr and Ghazala Khan, the parents of a fallen a U.S. Army captain who spoke out at the Democratic National Convention.

Obama made his remarks at a joint press conference with Singapore Prime Minister Lee Hsien Loong.

He noted that a pattern has emerged. Each time Trump says something that appears beyond the pale, Republican leaders scurry to disavow and distance themselves from his statements.

“If you are repeatedly having to say in very strong terms that what he said is unacceptable, why are you still endorsing him?” Obama asked of GOPers. “What does this say about your party that this is your standard-bearer?”

While some Republicans have so far declined to endorse Trump, today was the first time a sitting House GOP member came out and said that he would be voting for Democratic nominee Hillary Clinton.

Three-term Congressman Richard Hanna (R-NY) said that Trump is “unfit to serve our party and cannot lead this country.” Hanna had previously said he wouldn’t support Trump. He is not running for reelection this November.

But Trump’s allies are already ginning up concerns that Democrats are trying to steal the election. Longtime Trump adviser Roger Stone promised a “bloodbath” if Trump doesn’t win due to voter fraud.

“If there’s voter fraud, this election will be illegitimate, the election of the winner will be illegitimate, we will have a constitutional crisis, widespread civil disobedience, and the government will no longer be the government,” Stone said on a Breitbart podcast.