What happens when a marriage of convenience becomes inconvenient? A divorce, usually.

President Trump and the GOP establishment in Washington, D.C., aren't getting a divorce — yet — but a growing number of signs emanating from Republicans in Congress suggest they no longer find their alliance with the president all that convenient. When it comes to policy, it seems Trump is increasingly finding himself the loneliest man in Washington.

Consider these developments in recent days:

Sen. Chuck Grassley (R-Iowa), the Republican chairman of the Senate Finance Committee, on Wednesday called on Trump to lift tariffs on Canada and Mexico before Congress begins debating the NAFTA-replacement treaty the administration recently negotiated, citing the toll the trade war with those countries is taking on American farmers.

"We'll be working all hands on deck to get the job done," Grassley said. "But we need the administration to help us pave the way."

On a related front, Republican Sen. Pat Toomey (R-Pa.) on Wednesday announced bipartisan legislation that would let Congress reclaim its tariff authorities from the president. Other senators who have signed on to cosponsor the bill include farm state Republicans such as Ben Sasse (Neb.), Jerry Moran (Kan.), James Lankford (Okla.), and Lamar Alexander (Tenn.).

"The imposition of these taxes, under the false pretense of national security, is weakening our economy, threatening American jobs, and eroding our credibility with other nations," Toomey said in a press release announcing the bill.

Meanwhile, Politico reported Wednesday that Senate Majority Leader Mitch McConnell (R-Ky.) is signaling that he won't allow another government shutdown, despite the president's wish to have the option if Congress doesn't approve money for his proposed border wall during negotiations over the next few weeks. McConnell is even entertaining bills that would end shutdowns forever, according to the report.

The dissent even extends to foreign policy, where McConnell on Tuesday "effectively rebuked the president" by introducing a measure criticizing the "precipitous" withdrawal of American troops from Afghanistan and Syria. "We are not the world's policeman," the senator said. "But we are the leader of the free world. And it is incumbent upon the United States to lead."

What's going on here?

The president is starting to look like a loser.

The rout by House Democrats in November was a clear sign that Americans are fed up with Trump's shtick. The December resignation of Defense Secretary James Mattis — after Trump announced the withdrawal of troops from Syria — demonstrated limits to the GOP establishment's willingness to follow the president's whims. Then came the shutdown over the border wall, and Trump's surrender: His most vaunted skill — dealmaking — failed him on his favorite issue. It wasn't a good look.

All of this losing is taking a toll: The GOP's favorability ratings have dropped in recent months. A recent CNN poll suggests the president — never that popular with the broader publicis losing support among white working class voters who have usually given him their backing. A new Washington Post-ABC News poll shows a third of Republicans want to see a different presidential nominee in 2020.

Does all this mean the GOP establishment is ready to throw Trump under the bus? No. Not yet, anyway. But if he continues on this losing streak, and if Trump's trade policies keep hitting their constituents' pocketbooks, the temptation for Republican members of Congress to declare their independence from an unpopular president is only going to grow.

The partnership has always been fragile. While Republican leaders have rarely overtly criticized the president, they have occasionally — and carefully — let it be known they don't like his approach to politics. That's not to their credit: They seemed happy enough to go along with Trump as long as his presence in the Oval Office made it easier for them to pass tax cuts and confirm conservative judges to the judiciary. The main reason to abandon him at this point is because he is no longer of use.

There are limits to these new signs of dissent. Republicans in Congress might be ready to challenge Trump on policy grounds, but it's less likely they'd step aside at this point to allow an impeachment drive by Democrats. Give it time, though. There's only so much losing that the establishment GOP can tolerate.