Donald J. Trump’s latest Twitter tantrum bodes potentially disastrous for a legislative goal he and congressional Republicans have established.

They want to repeal and replace the Affordable Care Act. A U.S. Senate bill is hanging by a thread. Senators postponed their vote on it until after the Fourth of July recess.

So what does the president do? He fires off a vulgar, insulting tweet this morning about two MSBNC talk show hosts, ratcheting up his idiotic war against the media. The tweet makes some bizarre reference to Mika Brzezinski “bleeding badly from a facelift.” He refers to her as “Crazy Mika” and her co-host Joe Scarborough as “Psycho Joe.”

Republicans upon whom the president depends to help him approve this ACA repeal/replace idea now are running like thieves away from Trump.

It’s fair to wonder: Is the president’s lack of discipline, decorum and dignity going to cost him a victory that — frankly, it must be said — was tenuous?

This is no way at all at how you govern.