Democrats have flipped the US Senate and House of Representatives in a massive rebuke of Republicans and Donald Trump’s agenda. With Democrats majorities in both chambers, the final two years of Trump’s presidency will look markedly different from the first half. But what can Democrats actually do with with congressional power?

What can Democrats do with a House majority? After a string of wins in Republican districts across the country pushed Democrats past the 218-seat threshold needed to capture a majority, Hakeem Jeffries is poised to become majority leader and Republicans will lose their ability to pass legislation through the chamber without Democratic support. A Democratic majority can launch investigations into the administration, demand documents and testimony and subject senior officials to sustained congressional scrutiny. They might also come under pressure from their support base to impeach Trump for a third time.

The Senate confirms cabinet officials, ambassadors and federal judges, including supreme court nominees. A Democratic majority can block or delay many of Trump’s appointments and force the White House to negotiate over legislation.

What will Democrats investigate? Political reporter Joseph Gedeon laid out the most consequential investigations Democrats could launch. Here are a few of the investigations:

The family business: Robert Garcia, the top Democrat on the House oversight committee, has ranked Trump family corruption first on his list of priorities, while Representative Jamie Raskin has requested information on the business dealings of Trump son-in-law Jared Kushner and son Donald Trump Jr.

Epstein and the emails: Thanks to a tag-team effort by Representatives Ro Khanna and Thomas Massie, the Department of Justice was forced to release millions of files related to Jeffrey Epstein last year. But off the bat, the justice department blew the legally mandated deadline to disclose the files. Then it released only about 3.5m pages of the 6m in its possession; it said it had deemed the rest duplicates. And there has been bipartisan consternation about heavy redactions in some places, and the apparently accidental disclosure of the names of victims in other places.

The justice department is now facing a lawsuit from journalist Katie Phang over many of these issues. Even under a Republican-controlled Congress, the oversight committee under its GOP chair, James Comer, has been a rare spot of bipartisan comity, with members of both sides routinely (but not always) acting in concert to subpoena witnesses and hold them in contempt when they don’t cooperate. Expect that to continue in any new Democratic Congress.

The Pentagon and the war: Jason Crow, a Colorado congressman who sits on the armed services and intelligence committees and co-chairs the House end corruption caucus, says he will start with the Pentagon, citing reports of defense money steered toward companies linked to the Trump family.

Impeachment: Jeffries says Democrats have ruled nothing out regarding impeachment this time around, while the current Republican House majority leader, Steve Scalise, predicts an attempt on “Day 1”. What did the Democrats do last time they flipped the House under Trump?

In 2018, halfway through Trump’s first term, the Democrats flipped the House of Representatives in a sweeping blue wave. House committees quickly launched dozens of inquiries into his businesses, his handling of the Russia probes and possible conflicts of interest.

Just over a year after the 2018 midterms, after months of leftwing calls for impeachment, the House voted mostly on party lines to impeach Trump.

Democrats had accused Trump of pursuing a scheme to cheat in the upcoming presidential election by pressuring Ukraine to manufacture bad news about Joe Biden and then blocking congressional oversight. Trump was later acquitted in the Republican-controlled Senate on both articles of impeachment.

In 2021, Trump was impeached – and acquitted – a second time for inciting the January 6 attack on the US Capitol.