The Trump administration has suffered multiple body blows over the past 10 days: the suspiciously timed firing of FBI Director James B. Comey, President Trump’s revelation that there may be “tapes” of his conversations with Comey, The Post’s scoop that Trump revealed highly classified information to Russia’s foreign minister and the New York Times’s story that he allegedly asked Comey to stop investigating disgraced former national security adviser Michael Flynn. It was capped off with Deputy Attorney General Rod J. Rosenstein’s announcement Wednesday that he was appointing former FBI director Robert S. Mueller III as a special prosecutor to oversee the investigation of alleged ties between Russia and the Trump campaign. With events moving so quickly and Trump blundering so publicly, his opponents may feel like the president could be out before too long.

But despite recent progress, opponents of the president need to buckle down. Republicans will likely slow-walk (or no-walk) this issue as long as they control both houses of Congress. That is Trump’s strongest defense — and GOP gerrymandering has made it far stronger.

Yes, the hits racked up so quickly that a few Republicans are beginning to publicly express doubts. A number of senators suggested they were troubled by the firing of Comey, with Sen. John McCain (R-Ariz.) saying he was “disappointed.” Sen. Bob Corker (R-Tenn.) declared that the administration is in a “downward spiral.” Reps. Justin Amash (R-Mich.) and Carlos Curbelo (R-Fla.) became the first Republican legislators to raise the specter of impeachment.

But Amash and Curbelo are very much in the minority of the caucus, and for the others talk is cheap. Only five GOP senators and 10 representatives have called for an independent investigation and/or special prosecutor — most in lukewarm terms. The five senators who claim they want an independent investigation or special prosecutor — McCain, Lindsey O. Graham (S.C.), Susan Collins (Maine), Lisa Murkowski (Alaska) and Dean Heller (Nev.) — could ally with the Democrats to force one if they wanted, but there’s no sign of that. Already the excuses for inaction appear: After Rosenstein briefed the full Senate Thursday, Graham said that Mueller’s appointment “pretty much shuts Congress down. … Now we’ll just move on. We’re not prosecutors.” This is absurd: Special prosecutors or independent counsels have existed alongside separate congressional committees many times, including Watergate and the Iran-Contra affair. And Rosenstein’s association with Comey’s firing makes the existence of a congressional committee even more crucial.

Whatever the pretext, it remains highly unlikely that Republicans will stop dragging their feet on any Trump-related investigation. The history of past scandals such as Watergate also suggest that Trump’s situation will need to be far more dire before a Republican-controlled Congress would ever consider pushing back against the president.

So Democrats will need to retake at least either the House or the Senate to force things forward. In the Senate, bad luck made the Democrats’ path very tough. Despite needing just three seats to capture the upper chamber, all but two of the Republican-held seats up for reelection are in deep-red states. Worse, Democrats have to defend seats in five states that voted for both Romney and Trump.

Which brings us to the House and the most underappreciated aspect of what’s propping up the Trump presidency: gerrymandering. Democrats need 24 seats to retake the House, and a new report from the Brennan Center estimates that “in the 26 states that account for 85 percent of congressional districts, Republicans derive a net benefit of at least 16-17 congressional seats in the current Congress from partisan bias.”

Congressional district maps were last redrawn after the 2010 Census — right when the tea party wave handed Republicans increased majorities in state legislatures, which meant control in more states over the new district lines. Thanks to technology, it’s easier than ever for one party to create new districts that maximize its seat share. In North Carolina in 2016, for example, Republican candidates received 53 percent of the total votes for the House, but won 10 of the 13 congressional seats. The results have been most pronounced in swing states; the report’s authors Laura Royden and Michael Li estimate that GOP-drawn maps in North Carolina, Michigan and Pennsylvania have netted Republicans between two and three seats on average in each state. (Some Democrats have played games as well: Royden and Li also estimate that Democratic gerrymandering in Maryland and Massachusetts cost the GOP a few seats.)

The GOP’s trickery means that instead of picking off a few Republicans here and there, Democrats need a wave to retake the House in 2018 and start honest oversight of the Trump White House. Such a wave is plausible given the Trump administration’s troubles — and the related difficulties Republicans have had enacting their agenda. But it’s equally plausible that gerrymandering could save Trump from a Democratic House. Trump opponents hoping for a quick conclusion should steel themselves for a long fight. And when congressional districts are redrawn again after the 2020 Census, Democrats — and honest Republicans — should back districts drawn in neutral fashion that actually reflect the will of the voters.