How Donald Trump Could Send Republicans Crashing Down

But the videotape fits all of the major criteria for a damaging scandal, and it puts congressional Republicans in a precarious position.

It fits the Democrats’ contention that Mr. Trump is a misogynist. The Clinton campaign has been laying the groundwork for weeks with ads about his statements about women.

■ The scandal is easy to explain and can be turned into new television advertisements, although in this case it is probably unnecessary.

.. In August 2012, Claire McCaskill and Todd Akin were in a competitive Missouri Senate race before Mr. Akin, the Republican candidate, said that victims of what he called “legitimate rape” very rarely became pregnant.

.. Over all, he lost about 20 percent of the voters who supported Mr. Romney, according to exit polls.

.. It’s not clear to me that Mrs. Clinton could approach anything like 55 percent of the vote, given her high unfavorable ratings, even in a total Trump collapse.

.. Then came Mark Foley. In late September, it was revealed that Mr. Foley, a Republican congressman, had sent lewd messages to former congressional pages. At least some House Republicans were aware of it, and didn’t do anything

.. The underlying vulnerability in each case — George W. Bush and Mr. Trump — did not go away. But it really seemed as if the 2016 G.O.P. could dodge the worst of it

..Mr. Trump poses a more difficult challenge for Republican officials than Mr. Foley did: There was no cost to repudiating Mr. Foley, but the decision on whether to repudiate Mr. Trump puts Republicans in the unenviable position of alienating either Mr. Trump’s fervent base or moderate voters.