When the Republican Party backed a Democrat to stop their leading candidate

Republicans today can learn a lesson from the 1990 Louisiana race for U.S. Senator. This is from Wikipedia (but the bolding is mine)
https://en.wikipedia.org/wiki/United_States_Senate_election_in_Louisiana,_1990

"This election was viewed at the onset as potentially competitive, as Senator Johnston was viewed as vulnerable in light of Louisiana's economic troubles at the time and Senator Johnston's voting record viewed by Republicans as too liberal. The Republican Party leadership endorsed the (primary) candidacy of State Senator Ben Bagert...

...(David) Duke attracted national attention to the race with his involvement with white supremacist groups and his appeals to white resentment over affirmative-action programs. With Bagert failing to gain traction, the National Republican Senatorial Committee tried to recruit former Governor David Treen to jump into the race. When Treen passed, the effort turned from supporting Bagert to stopping Duke.[2]

As the election drew near, polls showed Johnston firmly in first place, with Duke in second place and Bagert trailing far behind at third. National Republicans grew fearful that Bagert's candidacy would only serve to force a runoff and that a potential runoff election with Duke being the de facto Republican nominee would hurt the national brand. On October 4, eight Republican Senators endorsed Senator Johnston, with Senator John Danforth saying at the press conference that "all of us would be embarrassed and mortified to have to serve in the United States Senate with David Duke masquerading as a Republican." Bagert dropped out of the race the next day, announcing that "it became more and more apparent, that instead of forcing a runoff between myself and Bennett Johnston, I might very well be forcing a runoff between somebody else and Bennett Johnston." He (Bagert) announced he would "reluctantly" vote for Johnston.[3] Bagert's name remained on the ballot, but under state law his votes could not be counted as part of the official tally.[4] After Bagert dropped out, HUD Secretary Jack Kemp endorsed Johnston, saying "there's no place in the Republican Party for someone who has practiced and practices racism, bigotry and anti-Semitism."

Today's national Republican Party faces a similar moment of truth. Will they stand behind a candidate who boasts about assaulting women, or back the only plausible candidate - Hillary Clinton, who stands between Trump and the Presidency? I'm expecting an epic fail from them on this.