Democratic control will bring two new advantages in the war on Trump. First, congressional committees hold an arsenal of investigative tools that can be called on with only majority-party assent. Chief among them is Congress’s subpoena power—its ability to compel the production of documents or the sworn testimony of witnesses in furtherance of a congressional investigation. That power can be exercised to produce anything from Trump’s much-discussed but as yet unseen tax returns to public testimony from his senior staff and family members (especially those who fit both descriptions). Moreover, due to a 2015 rule change pushed through by House Republicans, most House committees can now issue subpoenas on the authority of the chairperson alone, including three of the committees most likely to go after Trump: Oversight, Intelligence, and Foreign Affairs.
Second, Congress has the power to draw the results of any investigation into the harsh light of public scrutiny. The Watergate hearings were instrumental in bringing down Nixon because they forced Republicans to contend with damning testimony from the president’s closest aides, broadcast in prime time. Only once his approval among Republicans sank into the 50s were GOP congressmen willing to join the impeachment effort. Removing Trump from office before his term expires would require a similar loss of intraparty support. Since Democrats today don’t control the Senate—let alone hold the two-thirds majority required for conviction on House impeachment charges—it’s all the more important for them to erode the president’s base of support before attempting impeachment. Republicans’ impeachment of Bill Clinton increased his approval rating as those on the left rallied around him. Today, Democrats would do well to keep their fingers off the trigger until the president’s approval has begun to crumble.