President Trump has always liked tariffs. Now he seems to love them. They are increasingly his go-to tool for getting stuff done. Want to ensure China's leader comes to a summit? Threaten to ramp up the U.S.-China trade war. Hope to slow immigration into the country? Let other nations know you'll wreck their economies if they don't help stop the flow of people. Think the French should drink more American wine? Talk about slapping a levy on Bordeaux imports. For Trump, tariffs — and the threat of tariffs — are "a beautiful thing."

You probably haven't thought this much about tariffs since you wrote your eighth-grade history paper on 19th-century mercantilism. Of course, not everybody's a fan: Republicans in Congress, for example, seem to hate tariffs, which means they may soon have a choice to make.

On one hand, Trump is an incredibly popular figure among their constituents, which means that most Senate Republicans have to show some loyalty to him if they want to avoid a primary challenge. On the other hand, lots of GOP officials — and their rich donors — remain believers in their party's devotion to free trade, no matter what Tucker Carlson says.

So far, elected Republicans have managed to avoid making a choice between their devotion to free trade and their devotion to the president. They've been helped along by circumstance — the U.S. and Mexico apparently came to an immigration agreement over the weekend just before the president could impose some of his latest threatened tariffs — but also by good old-fashioned pork-barrel politics: American victims of the president's tariff mania have been paid off by taxpayers to limit the domestic damage done.

That has allowed Senate Republicans to grit their teeth and bear Trump's overuse of a policy tool they plainly hate. "I don't like it, but I'm going to support the president," Sen. Rick Scott (R-Fla.) said after the Mexico standoff. "I want border security."

But the whole ordeal revealed the fragile state of GOP deference. After the president announced his plan, Senate Majority Leader Mitch McConnell (R-Ky.) let it be known there wasn't much support from the chamber's Republicans. Sen. Cory Gardner (R-Colo.) warned the tariffs could hurt the economy. Even Sen. Ted Cruz (R-Texas) sounded like he was ready to revolt. "There's no reason for Texas farmers and ranchers and manufacturers and small businesses to pay the price of massive new taxes," he told reporters.

The GOP rebellion was called off this time, but the president's growing fondness for tariffs means he's likely to spark another showdown with his party in the near future.

Trump, after all, doesn't truly have tariff power: The Constitution gives Congress the sole power of taxation. But Congress has delegated that authority to the president, which means Congress can also take it away. Democrats who control the House of Representatives are presumably ready and willing to cut off Trump's authority as soon as it's feasible. That could happen if Democrats retake the Senate in 2020, but it could also happen sooner if Senate Republicans, faced with a decision between party loyalty and helping Congress reclaim its power, choose the former.

Trump should be worried.

"I'm more of an 'open-the-markets' kind of guy rather than look for ways to close those markets,'' Sen. Roy Blunt (R-Mo.) said this week. Many of his colleagues have made similar comments of late.

Disempowering the president would probably be very unpopular with Republican primary voters. But would it be less popular than stripping voters of their jobs and incomes? Studies suggest a 5 percent tariff on Mexican goods could cost more than 400,000 jobs at home, while another estimate suggests that tariffs on Chinese goods could end up costing every American household roughly $500.

That means that members of Congress may soon have to decide between loyalty to the president and the economic health of their constituents. The president will keep threatening tariffs until somebody makes him stop. That choice, ultimately, is up to Senate Republicans.