Democrats are projected to win at least 55 Senate seats, possibly 56 if Mary Peltola defeats Dan Sullivan in Alaska, and have 255 called House races with 11 still undecided, putting their House majority on track to be their largest since 2008.

Even with majorities in both chambers, Democrats will need Republican support for most legislation: Senate bills generally need 60 votes to end debate, and Trump can veto bills unless two-thirds of each chamber votes to override him.

Trump has signaled he plans to use his veto, and an override would require 290 House votes and 67 Senate votes if every member votes; based on races called so far, as many as 35 House Republicans and 11 or 12 Senate Republicans would need to break with him.

That kind of cross-party support may be difficult to secure, as Republicans are divided over compromise and Representative Jim Jordan, a founding House Freedom Caucus chairman, was chosen to lead the House minority.

Senate Majority Leader Chuck Schumer plans to use budget reconciliation to pass some measures with a simple majority, but the process is limited to taxes, spending and the debt limit, and any bill still needs Trump’s signature.

Newly elected Democrats from competitive districts and states could play an important role in negotiations, since many campaigned on cost-of-living and corruption issues and may help attract Republican support or shape bills Trump would sign.

Democrats will also have significant institutional leverage through committee chairmanships, oversight hearings and subpoenas, as well as control over which of Trump’s nominees the Senate confirms; Republicans are seeking to confirm 23 judicial nominees and nearly 100 executive nominees before Democrats take over on January 3.

Before that changeover, the current Congress must fund the government before its stopgap law expires on December 11, and disagreements—including proposals to cut off funding for the war in Iran—could trigger a shutdown that extends into the new Congress.

The last successful override of a Trump veto came on January 1, 2021, when Congress overturned his veto of the annual defense bill by votes of 322–87 in the House and 81–13 in the Senate.

Democrats can set Washington’s agenda, but turning it into law will depend on bipartisan dealmaking, with the incoming Democratic caucus including more potentially cooperative members than the previous one.