DEM 2016 Convention

Khizr Khan, father of fallen US Army Capt. Humayun S. M. Khan and his wife Ghazala speak during the final day of the Democratic National Convention in Philadelphia last week.

(Associated Press Photo)

The war of words between Republican presidential nominee Donald Trump and the Muslim parents of a fallen U.S. soldier seems to be getting worse.

It began at last week's Democratic National Convention in Philadelphia, when the soldier's father, Khizr Khan blasted Trump on his proposals to limit emigration by Muslims and asked him if he had ever read the Constitution.

Trump's usual political tool kit has appeared to fail him. He earned no reprieve with his complaints that Khan had been unfair to him; on Sunday morning, he claimed on Twitter that Khan had "viciously attacked" him. Trump and his advisers tried repeatedly to change the subject to Islamic terrorism, to no avail.

Trump also risked reopening controversies related to religious tolerance and military service: His treatment of the Khans has already brought on a new wave of criticism of his proposal to ban Muslim immigration, as well as of his mockery of Senator John McCain's time as a prisoner of war in Vietnam.

Democratic leaders and candidates for Congress began over the weekend to call on Republicans to disavow Trump. And the top two Republicans in Congress, House Speaker Paul D. Ryan and Mitch McConnell, the Senate majority leader, signaled their strong disagreement with Mr. Trump, but stopped short of condemning him in blunt terms.

Saturday's results: