Demonstrators march down Pennsylvania Avenue toward the Capitol during a June protest on separating families. (Toya Sarno Jordan/Bloomberg News)

Let's set aside the secret recording of Donald Trump and his then-lawyer talking about paying off a woman with whom he allegedly had an affair. The list of humiliations that President Trump has forced Republicans in Congress to deal with on policy alone is getting longer by the day — and some in the party have had it.

But it's still an open question what, if anything, will motivate Republican leaders to start wielding legislation to combat the things Trump does with which they fundamentally disagree.

This tweet Tuesday night from libertarian-leaning Rep. Justin Amash (R-Mich.) is the latest Republican cry to rein in Trump:

Amash is a regular Trump critic, so it's not a surprise he's publicly bashing both Trump's controversial tariffs, which run counter to Republicans' traditional free-trade orthodoxy, and Trump's decision to aid farmers hurt by those tariffs — a big-government-like move, that, you guessed it, is the opposite of Republicans' small-government philosophy.

What is new here is where Amash is putting the blame: On his own party in Congress. Trump, by now, is going to be Trump, most lawmakers figure. There's no changing him or altering his agenda. Lawmakers have tried to negotiate with him on immigration, keeping the government open, and much more — and failed.

That has spurred a movement among Trump's GOP dissidents in Congress to start putting up roadblocks to his ability to make them swallow policies with which they so strongly disagree.

Except Amash and others like him seem out of luck.

Look at last week, when Trump equivocated between Russian President Vladimir Putin and U.S. intelligence analysts on whether Russia tried to sway the presidential election.

A number of GOP lawmakers desperately wanted to respond, and they got airtime in a news conference the next day with Senate Majority Leader Mitch McConnell (R-Ky.). Most notable was Sen. Marco Rubio's (R-Fla.) bipartisan bill to punish Russia for election interference. A number of Republicans signed on after the Putin summit.

The Senate ended up unanimously passing a resolution to oppose one of Trump's most egregious potential deals with Putin, sending Americans abroad for questioning by Russian authorities. It was symbolic, but the fact that they acted was news in itself.

Since then, things have stalled on Russia. Notable critics seemed to accept Trump's “clarification” on what he really meant about Putin being involved in election interference.

Sen. Jeff Flake (R-Ariz.) is repeatedly trying this week to get the Senate to pass a resolution he wrote with Sen. Christopher A. Coons (D-Del.) to affirm the intelligence community's determination that Russia interfered in the election and must be held accountable. They've brought it up twice and twice failed to get a vote.

“Russian interference in the 2016 election is not debatable,” an exasperated Flake said in a statement Wednesday. “This resolution is nothing more than simply to say ‘it happened’. We know it happened, and we stand with our intelligence communities.”

Flake also seems out of luck.

This week, Trump gave Republicans in Congress a new reason to cringe. Despite strong warnings from members of Congress, he has  already gone full-steam-ahead on putting tariffs on products from China and U.S. allies such as Canada and the European Union.

The timing of those tariffs couldn't have been worse for Republicans, who are trying to keep both chambers of Congress in November. Trump's own former economic adviser, Gary Cohn, acknowledged the tariffs could undercut any benefit Americans see from a tax bill Republicans passed last year.

But on Wednesday, Trump managed to make it worse from Republicans' perspective. Trump did the equivalent of a mea culpa on tariffs when his administration announced they'd be handing out $12 billion to help farmers weather the storm.

Some Republicans, led by Sen. Bob Corker (R-Tenn.), have urged Congress to act quickly to rein in Trump's ability to unilaterally issue tariffs. He has been repeatedly rejected. This week, a frustrated Corker slammed Trump's aid for farmers with the one word Republicans perhaps hate most: “welfare.”

Corker seems out of luck.

We haven't even gotten into Trump's self-inflicted crisis on separating migrant families from their children, which Republicans feared would give the impression their party is openly hostile to immigrants. There, too, Congress briefly considered acting until Trump ended the policy. And what about Trump's announcement Monday that he's considering revoking the security clearance of top intelligence officials who have criticized him?

The direct contradictions to Republican orthodoxy are coming so fast from the White House right now that Speaker Paul D. Ryan (R-Wis.) appeared to throw up his hands on Tuesday.

“I think he's trolling people, honestly,” Ryan told reporters when asked to react to Trump's security clearance threat, a move that Corker had just compared to that of a “banana republic” like Venezuela.

It was a remarkably candid moment from Ryan that sounded the equivalent of: What do you want me to do about it?

Congress, as Ryan will point out, has already forced Trump to sign onto sanctions on Russia. It passed a bill by a veto-proof majority last summer, and after dragging his feet, Trump implemented them. (Trump's administration now holds up those sanctions as Exhibit A on how it is tough on Russia.)

In that same Tuesday news conference, Ryan made clear he wouldn't invite Putin to address Congress if Putin came to huddle with Trump. Ryan also said — for the umpteenth time — he thinks tariffs are the wrong way to try to boost the U.S. economy.

But to a growing number of frustrated Republican lawmakers, words and one sanctions bill aren't enough. Their ranks are growing, but right now, it's not clear what, if anything, will be Congress's final straw to confront Trump.