President Trump with Canadian Prime Minister Justin Trudeau. (Saul Loeb/AFP/Getty Images)

President Trump's biggest weakness is that he doesn't know how to make deals.

That, as Business Insider's Josh Barro points out, seems to suggest a deep unfamiliarity with the urtext of the subject, “The Art of the Deal.” Trump should know that “the worst thing you can possibly do in a deal is seem desperate to make it.” But that's precisely what he has done, first with health care and now with infrastructure.

Indeed, the latest reports are that Trump is hoping to use the prospect of a big infrastructure package to woo Democrats to his side on tax reform, and, in the process, cut the recalcitrantly right-wing House Freedom Caucus out of any negotiations. He apparently doesn't want to deal with them anymore after they played a leading role in scuttling Trumpcare.

There's only one flaw in this plan. It's called reality.

First off, Trump has lost whatever leverage he might have once had over Democrats. If he'd started his term by telling them that he was going to do infrastructure, and it was up to them whether that was on some of their terms or all the GOP's, there's at least a chance that he could have pried a few Democratic votes loose. But, as you may have noticed, that's not how he started his term.

Instead, he did just about everything he could to alienate Democrats, from his, in their view, discriminatory travel ban to his attempt to undo their greatest legislative achievement of the last 40 years in Obamacare. More than that, though, Trump's inability to unite Republicans behind his health-care bill showed Democrats that they don't have to make a deal with him out of fear of him making an extremely conservative deal with the House Freedom Caucus. It turns out he can't make a deal with them at all. Kind of makes it hard to play the two sides off against each other.

President Trump has introduced his budget plan, but that's just the beginning of the appropriations process. The Washington Post's White House economic policy reporter Damian Paletta explains what happens next. (Video: Jenny Starrs/Photo: Jabin Botsford/The Washington Post)

If Trump wants Democratic votes, then, it's going to have to be entirely on Democratic terms, which, whether he realizes it or not, are quite different even when it comes to infrastructure. How is that possible? After all, aren't we just talking about building roads and bridges and airports and water systems and electrical grids? Well, yes. But the question is how to pay for it. Republicans want to give private-sector companies tax credits for building approved projects, which they then could charge people to use. Think toll roads, except for everything. Democrats, meanwhile, want the government to take advantage of its still historically low borrowing costs to build whatever we need itself. They're afraid that tax credits would only fund the most profitable projects, not the most necessary ones; that they'd mostly be a windfall for projects that were already going to happen, not promote new ones; and that the money would go to people close to Trump, not the ones who need it most.

The problem is Trump might lose one Republican vote for every Democratic one he gains if he does infrastructure the way they want.

Not that Trump has to worry about this. It probably won't even get that far. That's because Democrats have no incentive to help Trump pass popular legislation when his unpopularity helps them. Why turn him into the winning winner he ran as, who alone possesses the ability to break through the gridlock of Washington, when they can keep him as the losing loser he's governed as, who can't even get a bill through one chamber of Congress his party controls? They won't, at least not on terms that are remotely acceptable to Republicans.

That's what happens when everyone knows you can't afford to walk away from the negotiating table, say, because you have a 36 percent approval rating. Nobody will be afraid of your threats, everybody will call your bluff, and you will cave to whatever they want. That would at least get some deal done if you were only giving in to one set of demands, but when you're trying to give in to two or three mutually exclusive ones, you won't even get that.

You'll get nothing.