(Carolyn Kaster/Associated Press)
Opinion writer

Sometimes when President Trump says something false and ridiculous, you say to yourself, “I’m sure his supporters are just going to eat that up.” Other times, you find yourself asking, “Isn’t that too absurd even for them to believe?” Like this:

We’ll get to the caravan in a bit, but on the idea that everything Trump doesn’t like is the Democrats’ fault: Can he possibly think that will persuade anyone?

I don’t mean the general proposition that if you like Trump you should be angry at Democrats. I mean the specific idea that when, say, a group of migrants comes to the United States seeking asylum, not only is that the fault of the Democrats, but if it weren’t for their stonewalling, Trump would have solved the problem by now.

Because here’s the thing: Republicans control every center of power in Washington. They have the White House. They control the House. They control the Senate. They have the courts, to boot. So how is it that despite their complete lack of power, Democrats are managing to stop Trump from implementing his terrific immigration plan?

The answer is that they aren’t. The reason Trump hasn’t signed immigration legislation is that he can’t get Republicans themselves to agree on a set of reforms. As my colleague Greg Sargent noted last week, “the bigger package of ‘tough’ measures Trump favors to ‘solve’ the larger immigration problem — a border wall, deep cuts to legal immigration — got the fewest of any votes in the Senate, meaning his solutions don’t have enough Republican support to pass Congress.”

Trump can’t even get Republicans to agree to fund a border wall, the centerpiece of his presidential campaign.

It has always been obvious that Trump loves to take credit for everything good whether he had anything to do with it or not, and cast blame on others for everything bad even when it’s largely his fault. It will be entertaining to watch him deflect responsibility if Democrats take control of the House in the midterm elections. But the trouble with unified government is that it makes it really difficult to plausibly claim that the people in charge are powerless and the people with no power are actually running the show.

It’s no mystery why Trump is suddenly making an issue out of this group of migrants slowly walking their way north. As The Post reported, he “continues to consider immigration to be a political winner next month in helping turn out his conservative base for the midterm elections.”

And not without reason. After all, it was his xenophobia that made him stand out from the crowd of candidates in the 2016 presidential primaries, and helped motivate enough white voters to the polls to get him elected. In recent days, “Fox & Friends,” where Trump gets most of his information about the world, has put the caravan on heavy rotation. The hope is that dark warnings of a foreign horde coming to kill you and your family will get people angry and scared enough to come to the polls; Trump is throwing around ludicrous claims about this caravan being full of criminals and terrorists.

But since the Republicans are the ones running the government, there’s always the danger that voters will say, “Wait a minute — if this is such a problem, why haven’t you guys solved it?” That’s what Trump is trying to avert by explicitly saying that Democrats are to blame.

Here’s the truth: Republicans are never going to pass immigration reform, for a number of reasons, the most important of which is that they can’t reconcile the “tough” approach their base demands with the humane approach the broader electorate wants. So all that’s left is stirring up as much anger as possible while trying to direct that anger at the opposition.

That’s why we shouldn’t be surprised if a few days before the midterm election, Trump does something dramatic — like following through on his threat to send the military to the border — to make sure that immigration dominates news coverage right before the election. It has already become clear that touting his accomplishments isn’t getting the job of holding off a Democratic wave done. At this point, Democratic anger at him and the Republican Congress is a given, and Republicans haven’t shown that they’re going to stampede to the polls to thank the GOP for its tax cut.

So Trump needs something else to juice Republican turnout, and he falls back on what he always does: hate and fear. It might work, but the odds don’t look good. By the way, if it fails and Democrats take the House, at least for the next two years he’ll be able to say that Democrats really are stymieing his agenda.