WASHINGTON-Not sufficiently humiliated by his collapse as the early Republican presidential frontrunner, former Florida Gov. Jeb Bush has endorsed Texas Sen. Ted Cruz in an attempt to deny the nomination to Donald Trump.

In doing so, Bush has further diminished his onetime stature as the darling of the dying Grand Old Party establishment once represented by his father, President George H.W. Bush, and his brother, President George W. Bush.

Previously, Jeb Bush had preserved some stature among the old-timers by conspicuously offering himself as the initial Trump giant-killer. In his frontal assault on Trump as a fraudulent Republican and a brutal demagogue bent on destroying the party brand and reputation, he unfortunately became its sacrificial lamb at the polls.

Now, in throwing his support to Cruz, he has splashed cold water on the third surviving GOP candidate, Gov. John Kasich of Ohio, the longest of long shots, who remains in the race after scoring only a single primary victory in his home state.

Kasich not only kept his slim chances alive but in the process denied Trump Ohio’s 66 convention delegates. Had they gone to Trump, he almost certainly would be in the driver’s seat for the nomination now.

The Republican establishment’s backlash against Trump came into the open earlier this month when the party’s onetime nominee Mitt Romney called on Marco Rubio (whose candidacy was still alive at that point), Cruz and Kasich to support each other as the means of keeping available delegates out of Trump’s clutches. Bush, considering his strong anti-Trump views, could easily have supported Kasich rather than Cruz as the acceptable establishment candidate left in the pack after Rubio dropped out.

Instead, Jeb cast his lot a candidate known for his right-wing extremism, not to mention for the animosity he has cultivated among his fellow senators and the arrogance that has made him persona non grata in much of the old party establishment.

Before Jeb Bush plunged into the 2016 Republican presidential race, he had a wide reputation in party ranks as “the smart Bush.” It was thought by some he might as president redeem the family name and reputation that was so profoundly tarnished by George W.’s calamitous 2003 invasion of Iraq and the financial crisis of 2008.

The huge early advantage in fund-raising for Jeb’s campaign was seen within the GOP establishment as a clever replay of George W.’s winning strategy in the 2000 primary, when other Republican White House aspirants were effectively scared off, giving the former President Bush’s elder son a clear path to the nomination.

But the Jeb Bush money blitz did not take into account the outsider phenomenon of celebrity businessman Trump. Financing his own campaign and seizing on voter anger toward Washington in general and organized party politics in particular, Trump stampeded the large Republican field.

Early on, Trump saw the soft-spoken and courteous son and brother of two presidents as an easy mark. He repeatedly characterized g him as “a low-energy person” and made fun of his ill-advised campaign logo, “Jeb!” – borrowed from a previous governor and losing presidential candidate, Lamar! Alexander of Tennessee, now a sitting senator.

Whether it was that Republican voters in 2016 had had enough of the Bush “dynasty” or Jeb’s shortcomings as a candidate, stumbling early over questions about the Iraq invasion, Trump pounced with effect. Jeb plunged in the polls as The Donald caught fire.

If Trump somehow is stopped short of the GOP nomination at the Cleveland convention in July, Jeb Bush isn’t likely to get much credit for the outcome. Rather, he may be remembered as a nice guy who was no match for a brawling, profane interloper who took him to the cleaners by playing under his own ungentlemanly rules.

Editor’s note: Jules Witcover’s latest book is “The American Vice Presidency: From Irrelevance to Power,” published by Smithsonian Books. You can respond to this column at juleswitcover@comcast.net.