What are the possible outcomes of US midterms?

Americans will head to the polls Tuesday in midterm elections that could reshape Washington and determine how much room President Donald Trump has to pursue his agenda during his final two years in office.

All 435 seats in the House of Representatives and 35 of the Senate's 100 seats, including two special elections, are on the ballot.

Republicans currently control both chambers, holding 53 Senate seats against 45 Democrats and two independents aligned with them, as well as a narrow House majority.

Democrats need a net gain of four Senate seats to secure a majority, while 218 seats are required to control the House.

Election forecasts generally favor Democratic gains in the House, while the Senate race remains more competitive. An Oct. 29 forecast by Decision Desk HQ identifies Democratic control of both chambers and a divided Congress with a Democratic House and Republican Senate as the two leading scenarios.

Whatever the outcome, Trump will retain his presidential veto power and broad executive authority, limiting the extent to which a Democratic-controlled Congress could reverse his policies.

Here are the four possible outcomes of the US mid-term elections and what they could mean.

- Democrats win both the House and Senate

A Democratic victory in both chambers would represent the biggest change in Washington's political balance, giving the opposition control of Congress for the remainder of Trump's presidency.

Democrats would gain leadership of congressional committees, allowing them to launch investigations, hold hearings, issue subpoenas and demand testimony from senior administration officials.

Their oversight efforts could focus on Trump's immigration enforcement policies, the administration's handling of the Iran conflict, tariffs, government spending and other actions by the executive branch.

Control of both chambers would also allow Democrats to block much of Trump's legislative agenda, including efforts to enact further immigration restrictions, expand tax cuts and overhaul health care.

Democrats could advance their own legislation on health care, voting rights and other priorities, although Trump could veto such measures. Overriding a presidential veto requires a two-thirds majority in both chambers, a threshold Democrats would be unlikely to reach.

Perhaps the most significant difference would be control of the Senate, which has the power to confirm presidential nominees.

A Democratic majority could reject or delay Trump's appointments to federal courts, senior administration positions and potentially the Supreme Court, limiting his ability to shape the federal government.

Democrats would also have greater leverage in negotiations over government funding and the national debt, potentially forcing the White House to accept concessions to avoid shutdowns or other disruptions.

However, even with control of both chambers, Democrats would face the Senate's filibuster rules, which generally require 60 votes to advance most legislation.

- Democrats win the House, Republicans retain the Senate

A divided Congress would create a different set of challenges for Trump, with Democrats able to block legislation in the House but Republicans retaining control over Senate proceedings and presidential confirmations.

House Democrats could use their committee leadership and subpoena powers to investigate the administration, summon officials for questioning and examine government policies and spending.

They could also pass legislation challenging Trump's policies on immigration, health care and foreign affairs, although Republican control of the Senate would make it difficult for such measures to become law.

A Democratic-controlled House could initiate impeachment proceedings against Trump or other administration officials. However, conviction in the Senate would require a two-thirds vote, making it unlikely without substantial Republican support.

Separately, Senate Republicans could continue confirming Trump's judicial and executive nominees, preserving an important avenue for the administration to advance its priorities.

The House would also have considerable influence over federal spending, since funding legislation must pass both chambers.

This could lead to prolonged negotiations over government funding, the debt ceiling and the administration's priorities, raising the risk of legislative gridlock and government shutdowns.

Trump could continue implementing policies through executive orders and federal agencies, although his administration would face more aggressive congressional scrutiny and potentially tighter constraints on funding.

- Republicans retain both the House and Senate

If Republicans maintain control of both chambers, Trump would have a clearer path to pursue his remaining legislative priorities.

These could include additional immigration restrictions, tax measures, changes to health care and legislation supporting other administration policies.

Republican control of the Senate would also allow the party to continue advancing Trump's judicial and executive nominations.

However, narrow majorities, disagreements within the Republican Party and Senate procedural rules could still complicate efforts to pass major legislation.

- Republicans retain the House, Democrats win the Senate

The fourth outcome would leave Republicans in charge of the House while Democrats take control of the Senate.

Republicans could continue advancing Trump's legislative priorities through the House, but Democrats would have the power to block them in the Senate.

Democratic senators could also slow or reject presidential appointments and launch investigations through Senate committees.

Both parties would need to negotiate on government funding and other legislation, while Trump's ability to secure new laws would be substantially constrained.

Regardless of which party controls Congress, the newly elected lawmakers will take office in January 2027, setting the stage for the final two years of Trump's presidency and the run-up to the 2028 presidential election.