By Karen Tumulty, Washington Post

Only a year ago, Republicans were congratulating themselves on having the strongest field of presidential candidates in a generation — diverse, highly credentialed conservatives who might be the salvation of a party that had lost the popular vote in five of the past six elections.

But now, the question is how close the Grand Old Party will come to annihilating itself and what it stands for.

Donald Trump — dismissed by GOP elders for months as an entertaining fringe figure who would self-destruct — has staged a hostile takeover and rebranded the party in his own image. What is being left by the wayside is any sense of a Republican vision for the country or a set of shared principles that could carry the party forward. 

A substance-free shout-fest billed as a presidential debate Thursday night marked a new low in a campaign that has seen more than its share of them.

The increasingly prohibitive front-runner and his three remaining opponents spent nearly the entire two hours hurling insults back and forth, with Trump at one point making a reference to the size of his genitalia.

“My party is committing suicide on national television,” tweeted Jamie Johnson, an Iowa political operative who had been an adviser to former Texas governor Rick Perry, one of the dozen Republicans whose presidential campaigns have been incinerated by the Trump phenomenon. The latest, retired neurosurgeon Ben Carson, formally dropped out Friday.

Also Friday, Trump clarified earlier statements that as president, he would order the U.S. military to waterboard militants and carry out other acts that violate international law.

In a statement, he said he understands “that the United States is bound by laws and treaties and I will not order our military or other officials to violate those laws and will seek their advice on such matters.”

In Thursday’s debate, moderator Bret Baier had asked Trump what he would do if service members refused to comply with his orders for exteme measures. The candidate replied, “If I say do it, they’re going to do it. That’s what leadership is all about.”

Trump’s musings on torture were among the many remarks that have alarmed establishment Republicans as worrisome and reckless.

“Republicans in general tend to be a group of people who like to view themselves as serious, having decorum, being orderly, being thoughtful,” said Roger Porter, who served as a senior policy official in the White Houses of Ronald Reagan and George H.W. Bush and who is now a professor at Harvard University’s John F. Kennedy School of Government.