All that has changed with Mr. Trump as president. For Republicans, honor and integrity are now passé. We saw it again last week when the president’s longtime lawyer Michael Cohen — standing in court before a judge, under oath — implicated Mr. Trump in criminal activity, while his former campaign chairman was convicted in another courtroom on financial fraud charges. Most Republicans in Congress were either silent or came to Mr. Trump’s defense, which is how this tiresome drama now plays itself out.

It is a stunning turnabout. A party that once spoke with urgency and apparent conviction about the importance of ethical leadership — fidelity, honesty, honor, decency, good manners, setting a good example — has hitched its wagon to the most thoroughly and comprehensively corrupt individual who has ever been elected president. Some of the men who have been elected president have been unscrupulous in certain areas — infidelity, lying, dirty tricks, financial misdeeds — but we’ve never before had the full-spectrum corruption we see in the life of Donald Trump.

For many Republicans, this reality still hasn’t broken through. But facts that don’t penetrate the walls of an ideological silo are facts nonetheless. And the moral indictment against Mr. Trump is obvious and overwhelming. Corruption has been evident in Mr. Trump’s private and public life, in how he has treated his wives, in his business dealings and scams, in his pathological lying and cruelty, in his bullying and shamelessness, in his conspiracy-mongering and appeals to the darkest impulses of Americans. (Senator Bob Corker, a Republican, refers to the president’s race-based comments as a “base stimulator.”) Mr. Trump’s corruptions are ingrained, the result of a lifetime of habits. It was delusional to think he would change for the better once he became president.

Some of us who have been lifelong Republicans and previously served in Republican administrations held out a faint hope that our party would at some point say “Enough!”; that there would be some line Mr. Trump would cross, some boundary he would transgress, some norm he would shatter, some civic guardrail he would uproot, some action he would take, some scheme or scandal he would be involved in that would cause large numbers of Republicans to break with the president. No such luck. Mr. Trump’s corruptions have therefore become theirs. So far there’s been no bottom, and there may never be. It’s quite possible this should have been obvious to me much sooner than it was, that I was blinded to certain realities I should have recognized.

In any case, the Republican Party’s as-yet unbreakable attachment to Mr. Trump is coming at quite a cost. There is the rank hypocrisy, the squandered ability to venerate public character or criticize Democrats who lack it, and the damage to the white Evangelical movement, which has for the most part enthusiastically rallied to Mr. Trump and as a result has been largely discredited. There is also likely to be an electoral price to pay in November.