Can anybody recall a political party turning on their own candidate before?

I live in Madison and follow politics fairly closely, and I never heard anything close to this.

Paraphrase of a twitter discussion
[INDENT]Every 50 years or so one party or another has a political reallignment. This may be what we’re experiencing now. The Whigs collapsed due to slavery and reformed as the Republican Party.

xkcd: xkcd: Congress [/INDENT] This is a highly unusual election, but not unprecedented.
Certain third world dictators even brag about their virility from time to time, though I’ve never heard of one protesting about his penis size.

The Republican Party hasn’t really turned on their candidate. Trump is the front runner but he hasn’t gained enough delegates to be the nominee yet. So what the Republican Party is doing is trying to influence which candidate gets the nomination - and that’s normal politics. There are people in the Democratic Party right now who are trying to influence whether Hillary Clinton or Bernie Sanders gets their party’s nomination.

It won’t be unusual until Trump becomes the nominee. At that point, leaders in the Republican Party will have to decide if they want to close ranks and support Trump or renounce him and tell voters to vote for somebody other than a Republican (or to just stay home and not vote). Only that would represent turning on the party’s candidate.

I think what’s unusual is not the fact that individuals within the Republican Party are trying to influence the nomination process, but rather the manner that they are trying to influence it. Romney’s speech in particular is something I’ve never seen the likes of before. Imagine Al Gore giving a speech like that about Bernie Sanders. I can’t picture that happening.

Somebody on NPR this morning was asked if there was a historic precedent for Romney’s speech, and they came up with 1960: Harry Truman was no fan of Kennedy, and said that the nominating process was rigged. But after the convention he fell in line and campaigned for JFK.

In the election of 1896, free silver advocate William Jennings Bryan won the nomination at the convention, but a lot of the “Bourbon Democrats” who were the faction represented by outgoing President Grover Cleveland were against his 16:1 silver:gold minting scheme and against the faction he represented. So you had an outgoing Democratic President not endorse the Democratic nominee for President, and almost no Democratic newspapers or state party organizations endorsed Bryan, either.

I think the difference is that Trump is simply far more distasteful to many people than Romney was.

No one had to endorse Romney. Sure, there are plenty of pressures to do so, but any individual could have broken ranks. At the time he was not a very exciting candidate, but he wasn’t nearly as divisive as Trump was.

It’s not that they haven’t fallen in line yet - it is too early. It is not that lots of party leaders who backed someone else aren’t jumping on the bandwagon yet - that is normal too.
What isn’t normal is making commercials and soundbites for the Dems to use in the fall. Especially if you are not running. (If you are negative ads are normal.) I don’t remember such a case, and Truman opposing JFK fairly quietly certainly doesn’t qualify.
And I certainly don’t remember the powers that be doing this to McGovern. Things were way too fractured back then, but there was none of this hate.

In the Missouri Senate election of 2012, Clare McCaskill spent $2 million running ads saying “Todd Akin is too conservative for Missouri,” which provided a huge boost to Akin in the Republican primary. Akin then repaid McCaskill by uttering his famous “legitimate rape” line. A number of Republican leaders called on Akin to drop out of the race. He refused, and McCaskill won by a huge margin.

It boggles the mind that a good number of Republicans still think like Akin.

Republicans Are Becoming Team Rape Again This Season.

Idaho GOP Rep Is Big Fan Of Todd Akin, Covers His Smash Hit ‘Legitimate Rape’

In 2004 when John Edwards ran as VP with Kerry most of his fellow NC Democrats did not like him and would not be seen with him. Unlike most states NC has their state wide races in the same years as the presidential race.

I don’t recall if they turned on him during the election, but there is an argument the state republicans refused to work with CA Governor Schwarzenegger (in office 2003-2011) because he was too moderate.

“The voters”? Several of the primaries that Trump has won have been in states that do not enforce party line voting. This means that Trump has probably won several primaries based on people who are not actually Republicans who are sympathetic to Trump’s message or even people who oppose the Republican Party voting for Trump with the express intention of making Trump a nominee who will lose in November.

That is not “Democracy,” that is gamesmanship.

For that matter, the whole notion of the nominee being selected (nearly) exclusively though the primary system is rather recent, so the answer to the question in the title of this thread is No one has seen a party turning on its own because until recently it was not possible for an outsider to simply pretend that he was a member of the party and run (relying on votes from people who were not members of the party) in a way to prevent actual members of the party from gaining the nomination.

In the 2006 Connecticut senate election cycle, Joe Lieberman lost the democratic primary then ran as an independent beating both the democratic pick and the republican candidate. Hillary Clinton, Harry Reed, Chuck Schumer and Howard Dean among others called for Lieberman to quit the race. Lieberman was endorsed by most of the Republican hierarchy (perhaps hoping for party switch later?). While Lieberman was running as an independent - most considered him a democrat.

Then there was the strange candidacy of Alvin Greene.