Donald Trump is proud of his reputation as a master dealmaker. Congressional Republicans even like to bring it up to flatter him.

“He comes from the private sector where your business partner today isn’t always your business partner tomorrow,” Rep. Darryl Issa (R-CA) told the Washington Post. “Just because you’re one way today doesn’t mean you’re written off. That’s The Art of the Deal side.”

The reality, however, is that this is little more than thin excuse making for a president whose statements tend toward extreme incoherence. In a practical sense, Tuesday afternoon’s rushed meeting between Trump and the entire Senate GOP caucus simply served to once again clarify that when it comes to policymaking, Trump can’t close a deal to save his life.

Mitch McConnell’s draft health care legislation seemed to end the meeting with, if anything, less support than it had going into it. After all, given that the bill didn't have the votes to pass and that some kind of concessions were going to have to be made to someone to get it over the top, why not become a squeaky wheel and try to get some grease?

But getting the job done is going to be a task almost exclusively for McConnell himself. Meetings and phone calls with the president don’t help.

And all for one pretty simple reason: The president of the United States has no idea what he’s talking about.

Donald Trump doesn’t understand Trumpcare at all

Glenn Thrush and Jonathan Martin, reporting for the New York Times, detail a vast array of reasons Trump has been less-than-central to the Senate legislative process, mostly focusing on Trump’s poor personal relationship with many senators.

But it’s at the end of their article that they get to the real crux of the matter — Trump doesn’t know anything about the policy issues at stake:

A senator who supports the bill left the meeting at the White House with a sense that the president did not have a grasp of some basic elements of the Senate plan — and seemed especially confused when a moderate Republican complained that opponents of the bill would cast it as a massive tax break for the wealthy, according to an aide who received a detailed readout of the exchange. Mr. Trump said he planned to tackle tax reform later, ignoring the repeal’s tax implications, the staff member added.

Many assessments of the health care bill reveal that it is an enormous tax cut for wealthy households and corporations masquerading as health care policy. Understanding this is absolutely central to everything that senators are arguing about.

Absent those enormous tax cuts, it would be easy to modify the bill to have lower deductibles and more insurance coverage. But given the commitment to the tax cuts, it’s simply impossible for the bill to not be exactly what Trump said the House health bill was — “mean.”

Trump is simultaneously celebrating the House bill’s passage, pushing for a very similar bill in the Senate, denouncing the House bill as mean, remaining unfamiliar with the major provisions of the Senate bill, and urging everyone on Twitter to pass these bills he doesn’t understand and won’t defend in detail. It’s simply not possible for him to play a constructive dealmaking role.

He can threaten, cajole, or plead if he wants. But if a senator actually wants to see substantive changes made to the bill in exchange for his or her vote, he or she is going to have to talk to someone else — someone what knows what the legislation says.

Remarkably, this may not matter

This exact same dynamic was in play during the formation, breakdown, and ultimate re-formation of the House health care bill, and the president’s disengagement from the policymaking process turned out to be surprisingly unimportant.

It seems paradoxical that you could combine the party discipline needed to push controversial and unpopular legislation through on a party line vote with total disengagement on the part of the party’s top leader. But the Trump administration seems to feature just the right mix of chaos and conventionality to make it work. Both Vice President Mike Pence and Chief of Staff Reince Priebus are very conventional Republicans with deep ties to the congressional party. That seems to be good enough to ensure that Trump will take his cues from Paul Ryan and Mitch McConnell regardless of his personal instincts. Trump triumphed over the GOP’s leadership during the 2016 primary, but he has largely surrendered to them on policy questions.

The result is that deals get done — or not — by the party’s congressional leadership. The ability to legislate hinges on Ryan and McConnell being able to agree among themselves. Trump serves as an ineffectual figurehead, talking tough but not really being able to engage with the policy details enough to properly negotiate an unprecedented rollback of the welfare state.