Paul Ryan, potentially one of America’s greatest Speakers, strikes us as uncharacteristically off balance in the wake of Donald Trump’s emergence as the presumptive Republican nominee. It rings an off note for him to be publicly ruminating on whether he’ll back the likely Republican nominee for president. He’d be better off in a private meeting with Mr. Trump, going over what Congress is prepared to authorize the president to do.

This jumps out at us as we listen to Mr. Trump rattle on about how he wants to, say, cut taxes, renegotiate our foreign debts, rebuild the military, or deregulate business. That’s all great, but the Constitution (which Mr. Trump would, if elected, have to swear to preserve, protect, and defend) grants every one of those powers to the lanky Wisconsinite and his colleagues in the Congress.

Taxes? The Congress has the sole power to lay and collect taxes. Debts? No branch of the government save Congress has the power to borrow on the credit of the United States. Not a nickel. Borrowing is the second granted power. All these trade deals on which Mr. Trump thinks he can do a better job? It is Congress that has the power to regulate commerce with foreign nations (and among the states). That’s the third power granted to Congress.

The Donald wants to build a wall on the Mexican border? We’re against it, but we seem to be in the minority. He’s not going to be able to build so much as a picket fence without Congress. He wants to make Mexico pay for the wall and to convince them to do so by threatening interruptions in trade? He’s back to the third grant to Congress, the regulation of commerce with foreign nations. Mr. Ryan could say, “Forget it, I’m going fishing.”

Mr. Trump has plenty of incentive to treat with the Speaker. Including if he wants to rebuild the military. Were Mr. Trump elected president, he would be the commander-in-chief, for sure. When Geo. Washington, John Adams, Jas. Madison and the boys parceled out the powers, however, they decided to give the power to raise and support armies — and provide and maintain a navy — not to President Trump but to Paul Ryan & Co. Truculent of them, but there it is.

No matter for whom Americans vote, we are not going to be electing a king — or queen. The fact is that the major powers are held by Mr. Ryan and his colleagues. The Speaker of the moment agrees with Mr. Trump on almost every issue, save for protectionism on immigration and trade (on both of which we’re with Mr. Ryan). Even there, Mr. Trump has already signaled a willingness to find a deal. Mr. Ryan doesn’t need to say whether he’ll support the Republican nominee. He simply needs to exercise his enormous powers.