The way these things happen is simple and insidious. In this case, because Mr. Trump was their party’s nominee, many Republicans felt duty bound to defend him, even though they would from time to time call him out for his worst offenses. They also held out the hope that Mr. Trump would grow in office and become more presidential.

What happened is quite different: As Mr. Trump was elected and then inaugurated, Republicans became more and more reluctant to call him out and more and more vocal in defending him and attacking his critics; rather than weakening, their loyalty to him intensified. And the president, rather than becoming more responsible, has become less restrained, more volatile, more unhinged. The result is the ethical wreckage we saw on display Wednesday…

When this story is finally told — when the sordid details are revealed, the dots finally connected — the Republican Party will be the political and institutional version of Mr. Cohen, who squandered his integrity in the service of a man of borderless corruption.