Why do the US midterms matter for Trump and Congress? 

The United States midterms on November 3 are dominating national and international headlines.

The stakes of the election are high. The midterm race will determine which party controls the US Congress, and in turn, shape the direction of Trump’s final two years in office. It will also decide key state and local positions.

But notching big wins in the midterm election may not be enough to shake up the balance of power in Washington, DC.

To understand the implications of this year’s midterm election and what may come next, Al Jazeera has put together this simple primer.

Here’s why the US midterms matter at the federal level.

Battle for the US House of Representatives and US Senate

Midterm elections fall at the halfway point of a president’s term, meaning the executive office will not be on the ballot.

Front and centre will be the battle for control of Congress. Two chambers make up the US legislature: the House of Representatives and the Senate.

Because members of the House serve two-year terms, all 435 seats in the chamber are up for election on November 3. However, most races are already considered formalities, with a clear frontrunner.

That leaves only a handful of races — about 50 — to decide who will win the House majority.

While subject to change, nearly every reputable election prognosticator has predicted that Democrats will win control of the House, some by as many as 15 seats.

The Democrats have a slimmer chance of winning a majority in the Senate, however.

That chamber has only 100 seats. But because senators have staggered six-year terms, only 35 seats are up for election. Only about a dozen of those races are considered competitive.

Still, Democrats have seen their odds of seizing the Senate increase, as the number of competitive races has grown.

Left-wing candidates have made inroads in deep-red states like Texas and Kansas, creating more opportunities for the Democratic Party to claim a Senate majority this election cycle.

Because the US vice president breaks ties in the Senate, Democrats would need 51 seats to control the chamber.

What does party control mean?

Congress passes laws and approves federal budgets. But even if a party secures a majority in both chambers of Congress, it may not be enough to control the country’s legislative agenda.

Laws can pass by a simple majority in the House, but they typically need a supermajority of 60 votes in the Senate to overcome a process known as the filibuster. That process can allow a minority group to stall legislation indefinitely, barring a supermajority.

Therefore, unless a party wins more than 60 seats in the Senate, most legislation will still require at least some level of bipartisan support to pass.

Even if legislation passes both chambers, the president can veto any bill that comes across his desk. Overriding a presidential veto requires a two-thirds supermajority in both the House and the Senate.

Achieving the broad bipartisan support needed to overcome a presidential veto is exceedingly rare.

The last time it happened was in January 2021, during Trump’s first term. At the time, the US president had lost the 2020 election, and he saw his support from Republican lawmakers dissipate when he attempted to veto a defence spending bill.

Still, there are instances when bipartisan support overcomes presidential objections. A bill to increase the housing supply passed both the House and Senate with veto-proof majorities earlier this year, despite Trump’s stated opposition.

So what happens if Republicans maintain control of Congress?

Republicans currently hold two majorities in Congress, with 53 seats in the Senate and 218 in the House.

With Trump in the White House, that means the party has held a so-called government “trifecta” over the last two years, with three levers of power under its command.

The Republican majorities in Congress have helped Trump pass some of his signature legislation, including surging funding to Immigration and Customs Enforcement (ICE) and cleaving back some forms of publicly funded healthcare as part of a sweeping 2025 tax bill.

But Republicans’ numbers have not been enough to pass Trump’s entire legislative wishlist. Notably, he has been unable to pass his signature federal voter identification law, dubbed the “SAVE America Act“, amid Democratic opposition.

There have also been a handful of issues where Republicans have defied Trump, particularly on tariffs. A few Republicans have also voted to assert congressional authority over the US-Israel war with Iran.

If the Republican Party maintains control of both the House and Senate in November’s race, its majorities could continue to help Trump’s legislative agenda. But there is an important caveat.

Lawmakers will be keeping an anxious eye on voter sentiment as the 2028 elections approach. With Trump unable to seek a third term, some Republicans may have more appetite to publicly oppose the lame-duck president during the next two years, in order to boost their election prospects.

If Republicans maintain control of the Senate but lose the House, they would still be able to help Trump confirm his nominees for key federal roles.

Hundreds of federal positions require approval from a simple majority in the Senate, including roles in the judiciary, including Supreme Court justices.

What if Democrats take control?

The party in control of Congress, with a few exceptions, can determine what legislation is brought to a vote and when.

But for Democrats, the most significant outcome of winning a majority in one or both chambers would be the ability to block Trump from legislating his agenda over the next two years.

That said, analysts expect a Democrat-led Congress to take a largely defensive stance, batting down Trump’s proposals.

Going on offence — and passing their own legislative agenda — will be far more difficult, even if the party wins a majority in both the House and Senate. Democrat-led laws would still face Trump’s veto power.

However, holding majorities would help Democratic members slip policy priorities into “need-to-pass” funding legislation. The spectre of a government shutdown could pressure Republicans to pass budget bills, even if they do not agree on all the terms.

Democrats can also bring topics to a vote to force congressional Republicans to oppose popular policies or simply take a public stance on divisive issues.

House Minority Leader Hakeem Jeffries has laid out a 100-day plan for if Democrats take control of the chamber. Topping the agenda are votes on Trump-backed healthcare funding cuts, asserting congressional authority over the US-Israel war with Iran and rolling back Trump’s tariff programme.

Those issues have split the Republican base and would pose thorny dilemmas for lawmakers already posturing for the 2028 vote.

Will Democrats impeach Trump?

As Trump rallies on behalf of Republicans in the run-up to November’s vote, he has repeatedly expressed concern that Democratic control of Congress could lead to one eventuality: his third impeachment.

Trump was already impeached twice during his first term. “If we don’t win, they’ll end up impeaching me,” he told a rally in Durant, Oklahoma, in early October.

If Democrats do take control of the House or the Senate, they will take over leadership of dozens of committees. Through those committees, they can launch investigations — with subpoena power — into an array of subjects.

Some Democrats have already said probing allegations of Trump family corruption will be a top priority.

House lawmakers can also introduce articles of impeachment and ultimately vote to impeach federal officials, including the president, with a simple majority.

However, the Senate would need to vote to convict the official with a two-thirds majority before they can be removed from office.

Perhaps more significantly, if Democrats win control of the Senate, they would be able to block the confirmation of Trump appointees in key roles during his final two years in office.

So what will change on the war with Iran and the economy?

A Democratic surge is likely to signal discontent with the Trump administration, but there will not be a swift, tangible change on many of the issues that have defined the election season.

For example, if Democrats secure both majorities in Congress, they could assert their leverage to seek to address affordability issues, drilling into topics like housing, healthcare and the cost of living.

But they can do little to immediately change the myriad factors that led to the high price of petrol and groceries. Any gains would most likely be hard-fought, slow-coming and incremental.

The same is true for the US-Israel war with Iran.

Under the US Constitution, only Congress can declare war, something it has not done since World War II. Presidents have long used various legal arguments to circumvent that constitutional requirement.

Most recently, the Trump administration argued that the US-Israel war with Iran did not require authorisation from Congress because the president has a duty to protect the American people.

Trump has also argued that the war has started and stopped several times, each time renewing the 60-day window he has to receive Congress’s authorisation.

To reassert Congress’s authority to declare war, Democrats could pass a legally binding “war powers resolution” to rein in Trump, but they would need two-thirds support to overcome the presidential veto.

Even if a resolution were able to overcome the veto, experts say it is unclear how the US judiciary would respond if Trump were to flout Congress’s will.

Still, Democrats could use control of Congress to attempt to stifle any funding for the war.