The Republican Party this week is like 5th-century Rome must have been after the Visigoths stormed the city’s gates. Anarchy and confusion reign, there is the sound of anguished wailing, and political leaders are making an urgent calculation: Resistance or collaboration?

The suddenness of Donald Trump’s final victory over the GOP establishment was shocking. On Monday, Pollyannas were still convincing themselves that Trump could be thwarted at a contested convention. Within 48 hours, he had won the Indiana primary in a landslide and his last two opponents, Ted Cruz and John Kasich, had surrendered. Even Trump couldn’t have expected it to happen so fast.

But no one should be surprised, at this point, that the result of the Republican primary process is Donald J. Trump as the party’s presumptive nominee for president. He has been the clear front-runner for the better part of a year. Too many observers, both inside and outside the party, saw the race as they thought it should be, not as it was. They ignored the obvious fact that Trump was gaining momentum as the primaries went on. They believed it was unthinkable that he would win, so they gave too little weight to clear evidence that he was doing just that.

I mention these issues of perception only because I’m now seeing a lot of analysis predicting how easy-peasy it will be for likely Democratic nominee Hillary Clinton to wipe the floor with Trump in the fall. Anyone buying into this story line should first try to ascertain whether it’s based on reality or wishful thinking. As for me, I’ll continue not to take anything for granted.

Republican elected officials and party leaders do not have time for such retrospective contemplation. They have a decision to make. The party belongs to Trump now, just as Rome belonged to the barbarians, and GOP politicians have to decide whether to fall in line or take up arms against the new order.

Republican presidential candidate Donald Trump gave unusual advice to a crowd of West Virginia voters on May 5, saying "you don't have to vote anymore. Save your vote for the general election, okay? Forget this one. The primary is gone." (Reuters)

So far, GOP luminaries are mostly choosing collaboration over resistance — although many have so far declined comment and seem to be still pondering.

The biggest blows to Trump’s legitimacy as the standard-bearer of the party of Lincoln were struck by the two most recent Republican presidents. Spokesmen for George H.W. Bush and George W. Bush announced that 41 and 43 have no plans to endorse Trump — an extraordinary rebuke from the family that has defined the party since the era of Ronald Reagan.

House Speaker Paul D. Ryan (Wis.), asked if he was ready to endorse Trump, said that “I’m not there right now.” Massachusetts Gov. Charlie Baker said he would not vote for Trump — or for Clinton, a spokeswoman added. Sen. Ben Sasse (Neb.), who has vehemently opposed Trump, was unbowed in a lengthy Facebook post that called for a third-party candidate to emerge.

Most of the rest of the party, however, seems to be boarding the Trump train, even if it might be heading over a cliff.

Republican National Committee Chairman Reince Priebus set the tone Tuesday night just minutes after Cruz’s withdrawal with a tweet announcing that Trump was the presumptive nominee and that the party should unite behind him.

The most commonly stated position of prominent Republicans who have spoken thus far is that they will support “the nominee of the party.” For example, this is the view of Sen. John McCain (Ariz.), whom Trump cruelly ridiculed for being shot down and captured during the Vietnam War. According to Politico, McCain said at a fundraiser last month that his reelection bid “may be the race of my life” because of Trump’s vicious rhetoric about Latino immigrants.

Some other senators facing tough battles to hold on to their seats seemed to disappear into witness protection. One who emerged, but probably shouldn’t have, was Sen. Kelly Ayotte (N.H.), who tried to stake out the impossible position that she would “support” Trump but not “endorse” him. Sorry, senator, but that’s not even a distinction, much less a difference. You’re on board.

1 of 14 Full Screen Autoplay Close Skip Ad × These 10 Republicans refuse to vote for Donald Trump View Photos And they’ll tell you why. Caption And they’ll tell you why. Former Secretary of State Colin Powell “General Powell said at a meeting of the Long Island Association that he would be voting for Hillary Clinton,” a spokeswoman confirmed Oct. 25. Powell added in an interview that he picked Clinton “because I think she’s qualified, and the other gentleman is not qualified.” Nikki Kahn/The Washington Post Buy Photo Wait 1 second to continue.

South Carolina Gov. Nikki Haley also said she “will support the Republican nominee for president,” treating Trump’s name like that of Lord Voldemort. Then she hastened to add her name to the growing list of rising GOP stars who say they are not interested in being considered as you-know-who’s running mate.

What does “I support the nominee” buy you? Trump’s allegation that Mexican immigrants are “rapists.” His promise to deport 11 million people living here without papers. His pledge to ban Muslims from entering the country. His misogyny. His bigotry. His willful ignorance of foreign and domestic policy. And much, much more.

The emerging Republican message: We’re all Visigoths now.

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