The Post editorial: President Donald Trump must build coalitions after his heath care failure.

Donald Trump promised Coloradans this past summer that, if elected president of the United States, he would fix the gridlock in Washington and start getting things done.

Speaking — we assume — tongue in cheek, Trump promised Republicans at the Western Conservative Summit in Denver that he would lead the party to so many victories, Colorado conservatives would tire of the success.

And, of course, Trump also asserted on the trail that he alone could fix the nation’s problems, and he ranked repealing and replacing Obamacare a top priority.

But as the world watched last Friday, Trump’s strongman approach to reforming Obamacare failed spectacularly, even in the now Republican-controlled Washington, where House Republicans had been waiting for seven years to do the deed.

This was so much more than a bad beating for Trump and for the Grand Old Party. This was an epic, self-inflicted humiliation for the new president and an enormously costly setback for Republicans. There is no other way to view the collapse. Trump hoped to force the holdouts’ hand, when he should have understood he didn’t have the votes.

The irony is supreme. For seven years now, the narrative from the hard right has been that passage of the Affordable Care Act represented the pinnacle of runaway government overreach that must be neutered and tamed. The ACA fueled the Tea Party rebellion that led to a Trump presidency. During that time, House Republicans voted to repeal the ACA more than 60 times.

Yet somehow, the Republicans didn’t actually have a plan the party could rally behind. And, somehow, Trump wasn’t keen enough to realize the one thing that the hardliners in his party won’t do is say “yes” to anything they don’t fully agree with.

If Trump the dealmaker hopes to have much success with his ambitious agenda, he will need to start building the coalitions he needs to make deals and get the job done.

While he is at it, he should finally admit, at least to himself, that he needs to start acting presidential and learn — no matter how much he dislikes it — how Washington works.

Until he does so, who could blame more moderate or establishment Republicans for feeling like they needed to start putting some distance between them and the president?

Last week began with the directors from the FBI and the NSA stating in congressional testimony that Trump can’t be trusted regarding his claims that President Barack Obama illegally had his phones tapped. Federal investigations into Trump campaign contacts with Russian officials continue.

Neither of Trump’s Muslim bans made it through the courts.

As the Republican strategist Steve Schmidt told The New York Times, “No administration has ever been off to a worse 100-day start.”

Trump came into office with an ambitious agenda, and even Democrats say they are willing to try to make Obamacare better. Or they were saying that, when it looked like Republicans had all the tools they needed to reform the law in their image.

Now Trump’s enemies are emboldened. For much of the early days of his young presidency, Trump still enjoyed the element of surprise. There was a power in the cloud of confusion he created by trying to rush through big changes. That fog is lifting now.

If Trump wants to right the ship, he ought to look within.