On a steamy summer day in Washington, almost 43 years ago, an announcement by a freshman Virginia congressman sealed the fate of a president.

It was July 25, 1974, and Caldwell Butler, who rode to Congress on Richard Nixon’s coattails just two years earlier, told fellow members of the House Judiciary Committee that he would vote to impeach Nixon for the president’s role in the Watergate cover-up.

That announcement from a Republican congressman representing a reliably Republican district was widely regarded as a harbinger of Nixon’s political doom.

Today, Butler’s successor from that same Shenandoah Valley 6th Congressional District, Republican Bob Goodlatte, sits as chairman of that same House Judiciary Committee. Goodlatte has given no public indication he’s considering following Butler’s fateful path, even as official Washington churns with renewed talk of impeachment.

The current political climate in Washington is dominated by:

To some, this conjures up memories of Nixon-era obstruction of justice. But, with Republicans controlling Congress, it will be GOP lawmakers who play the pivotal role in deciding Trump’s future.

Several Republican-led congressional committees have launched investigations into the Russian affair. But Goodlatte has resisted Democrats’ calls for a probe thus far and has kept his House Judiciary Committee on the sidelines, requesting no documents and scheduling no meetings on the issue, despite the fact that his panel has oversight over the Justice Department and the FBI.

Goodlatte has deferred to the special counsel appointed by the Justice Department to investigate the Russian meddling, calling Robert S. Mueller III “a well-respected law enforcement professional” and noting he is confident that Mueller “will conduct a thorough and fair investigation.” No doubt, many Republicans were relieved at Mueller’s appointment, which relieves the pressure on them to act.

Caution has served Goodlatte well over the years. He was elected to Congress in 1992 and has been reelected a dozen times. His valley district is one of the most steadfast Republican strongholds in the nation. The 6th District stretches up the valley from Roanoke to just north of Luray. Its voters chose Republican Trump over Democrat Hillary Clinton 60 percent to 35 percent last year. One might reasonably ask, why would Goodlatte even consider getting out ahead of those voters, at least at the present?

Only Virginia’s 9th Congressional District, in the southwest corner of the commonwealth, gave Trump a bigger margin of victory: 69 percent vs. 27 percent for Clinton. It’s no wonder that Rep. Morgan Griffith, a Republican in his fourth term, is also largely quiet about Trump, and when he does speak, he’s mainly supportive.

Whether a member of Congress supports or opposes a president of the same party on an issue, political survival, not just party loyalty, is at stake. That’s why Rep. Barbara Comstock (R-10th) has an independent streak. She broke with Trump on the Republican plan to revise and repeal Obamacare. She also pointedly said she could not defend Trump’s firing of Comey. The reason is simple: Her district is politically competitive, stretching from the very blue D.C. suburbs to the red counties approaching the West Virginia line. The district gave Hillary Clinton a 10-percentage-point victory margin last year and came within a whisker of voting for Obama in 2012.

Polls show that most of the president’s core believers are sticking with him, but their numbers are beginning to shrink. With most Americans, Trump is unpopular, and the 2018 midterm elections are right around the corner.

Successful politicians are good at reading the numbers. When they see the tipping point approaching, it’s usually safe bet their positions will reflect the prevailing public mood.

Donald Trump was an outsider presidential candidate without a significant commitment to or history with the GOP. He has no reservoir of good will to draw from on Capitol Hill. Republicans in congress will stick with him as long as they are convinced it’s in their best interest. It’s nothing personal, it’s just business.

Mark J. Rozell is dean of the Schar School of Policy and Government at George Mason University.