Until today, the big question about Mr. Trump was when coverage would shift toward a serious examination of him. Journalists and campaigns have, understandably, been reluctant to treat him as a serious candidate. The Huffington Post, for instance, decided it would cover him in the entertainment section. But eventually, campaigns were bound to treat him as a threat to be neutralized, and journalists would decide he was a candidate who needed to be covered.
Today, Mr. Trump brought the shift upon himself. His comments were nothing less than an invitation for the rest of the Republican Party to begin their long-awaited offensive. So far, the Republican National Committee, Rick Perry, Bobby Jindal, Jeb Bush and Scott Walker have already criticized him for his comments.
After today, Republican commentators and campaigns will have far fewer reservations about attacking Mr. Trump. They will be dismissive of his candidacy, and they will probably diversity their attacks, expanding the onslaught to include his record of donating to Democrats and his continuing support for universal health care. Nearly all of the campaigns have incentives to pile on, and Mr. Trump — without a deep base of support and with few party allies — will struggle to hold on.