There's a theme to Trump's low points as President

The theme tying them together is his aversion to new people coming into the country. It was his top and most divisive issue as a candidate and the one that has most bedeviled his presidency.

These inflection points, the results of Trump's own words or his provocative executive actions, have often created crises where none existed.

Trump, in other words, has shown himself to be a President who can create thunderstorms. A week ago it would have been hard to imagine a scenario by which some Republican governors would be pulling their states' troops away from the border after Trump ordered them there, but Trump found it.

It's the decision by his administration to enact a "zero-tolerance" stance toward people crossing the border illegally, which has had the effect of taking children from the arms of their nonviolent parents, creating a new sort of border crisis to go alongside the one the Trump administration has long been saying is already there.

In a switch from his normal practice of not backing down under any circumstances, he walked partway back from the brink of the most recent controversy -- separating children from their undocumented parents trying to cross the border while the government prosecuted them -- with an executive order Wednesday that seems to say the parents and children would be detained together instead, if possible.

"OK. You're gonna have a lot of happy people," he said in the Oval Office, flanked by Vice President Mike Pence and Homeland Security Secretary Kirstjen Nielsen.

First was his attempt to enact a surprise ban on many Muslims entering the country and his subsequent firing of acting Attorney General Sally Yates, who refused to continue enacting it, setting off concerns of a constitutional crisis.

Subsequent versions of his executive order are still before the courts.

Also still before the courts is his stalled attempt to end the Deferred Action for Childhood Arrivals program, former President Barack Obama's effort to shield from deportation certain people brought as children to the US by undocumented immigrants.

Trump's DACA effort, which did not lead to a permanent legislative fix as the President demanded, set up a slow-moving mini-revolt of Republican moderates that is still playing out on Capitol Hill.

Trump didn't help that effort when he scuttled bipartisan proposals because he was frustrated by refugees from what he described behind closed doors to lawmakers as "shithole countries."

That terminology caused an international outcry, renewed complaints that the President of the US was being racist and deflated any chance for a bipartisan immigration bill at the time.

Now add to the difficulty of figuring out DACA the difficulty of figuring out how to deal with with young children on their way into the country illegally, which after Trump's executive order the US will now be figuring out how to detain together.

Trump has said multiple times he'd like to enact some kind of comprehensive immigration overhaul, presumably like the bills that have passed either the House or the Senate but not become law under Democratic and Republican presidents over the past 12 years.

He acknowledged the difficulty Wednesday when he pointed out that people have been trying and failing to do it for decades.

"This has been going on for 60 years," he said. "Sixty years, nobody's taken care of it. Nobody's had the political courage to take care of it. But we're going to take care of it. But it's been going -- it's been going on for a long time."

He did not mention that Ronald Reagan passed massive new border security measures along with what's today seen as an amnesty for undocumented immigrants in 1986. Or that George W. Bush signed a law to put up hundreds of miles of fencing. Or that Obama stepped up deportations, a baton Trump has taken further.

But none of those other Presidents tried to force action on Capitol Hill by making things more painful for immigrants, as Trump has done repeatedly.

A Gallup poll released Wednesday suggests most Americans (57%) oppose a border wall like the one Trump wants to build, but most Republicans (73%) favor it.

One bill Republicans are selling as a compromise among themselves would address DACA and the wall funding issue, but it still faces a difficult road and Democratic opposition would seem to make it a nonstarter in the House.

The most difficult thing -- and the one Trump keeps coming back to -- is the border wall he promised his faithful during the 2016 campaign, but which Republicans in Congress don't want. They're planning to send him a fraction of the money he needs to build it.

If they don't send him more, he could feasibly shut down the government. That would be another self-inflicted wound when Trump's party controls the entire government apparatus and they are headed into an election when control of the House, in particular, is up for grabs.