The crossfire between the two leading presidential candidates intensified Monday, as Democrat Hillary Clinton’s campaign stood by her claim that Republican front-runner Donald Trump’s rhetoric is being used as propaganda by terrorist groups, though there is no evidence Islamic State has put him in videos.

Mrs. Clinton said in Saturday’s Democratic debate that Mr. Trump “is becoming ISIS’s best recruiter,” and that he was being used in videos. Mr. Trump angrily denied the former secretary of state’s charge and demanded an apology from her. The Clinton campaign refused to provide one, pointing to comments from several counterterrorism experts and social media posts by terror groups to support the claims.

The spat across party lines represents a new phase in the presidential campaign for Mrs. Clinton, who has begun to sharpen her attacks on her Republican rivals, with Mr. Trump emerging as a top target.

Mrs. Clinton and her Democratic challengers mentioned Mr. Trump nine times in their Saturday debate—a sign of how he has come to dominate the political conversation on both sides of the aisle.

http://www.wsj.com/articles/trump-demands-apology-from-clinton-on-isis-debate-quip-1450721984