Barack H. Obama used to say it all the time: If Republicans have any improvements they want to make to the Affordable Care Act, I am willing to work it with them.

The Democratic president was open to tinkering with the ACA. He said he was keeping an open mind on ways to improve his signature piece of domestic legislation.

Then his time as president expired. His successor, Donald J. Trump, had vowed to “repeal and replace” the ACA starting with Day One of his presidency. He has labeled the ACA a “disaster.”

But the president can’t seem to bring himself to persuade his fellow Republicans in Congress to do as his predecessor has suggested regarding improving the ACA. They have dug in hard in their effort to repeal and replace the ACA. Trump has joined them. They now are left to fighting among themselves over the best way to replace the ACA.

The ACA is not the “disaster” that Trump has asserted about it. The law has provided health insurance for more than 20 million Americans who couldn’t afford it.

I am willing to concede that the ACA isn’t perfect. However, it is the law of the land. Why in the world can’t the GOP pick the law apart, huddle with Democrats, agree on what’s working and then seek to reform the elements of the ACA that aren’t working?

Oh, no. They cannot go there. The intention among the GOP leadership is to throw out every vestige of the ACA because, I’m going to presume, it has President Obama’s imprimatur. The Republican congressional caucus had declared its intention to make Obama “a one-term president,” and the ACA — approved in 2010 — simply had to go.

Tinkering and mending this law doesn’t constitute an unprecedented solution. Congress did as much with Medicare in the 1960s and with Social Security in the 1930s.

They managed — somehow — to improve those other two pieces of landmark legislation.

What about the here and now?