With control of Congress, here’s how Democrats could stop Trump’s war in Iran

The Democrats’ sweeping victory in the US midterm elections puts them in a stronger position to interfere with President Donald Trump’s agenda. This includes his deeply unpopular and costly war against Iran, which could be among their first priorities.

As president, Trump will be able to veto any legislation aimed at ending the war. But the Democrats still have another powerful card up their sleeves: cutting off funding for the war.

There are caveats, however. History suggests exercising this power could trigger a political confrontation that may backfire. And even if the Democrats succeed in ending the war, they may not be able to reverse the damage it has done to the US’ global standing.

The limits of legislation

Democrats will have three main options to try to force the war against Iran to a close. Two of these, however, face significant limitations.

The first – and perhaps most obvious – option is through legislation. There are a few different ways to do this.

One approach is to pass a resolution calling for an end to the war.

Congress already attempted this in June, passing a concurrent resolution (with the support of some Republicans) that directed the president to either withdraw US forces from hostilities against Iran or seek the approval of Congress before continuing. This was done under the War Powers Resolution of 1973.

These so-called concurrent resolutions are, however, widely seen as non-binding. Intended to express the opinion or will of Congress, they are generally used to deal with internal matters within Congress.

Trump ignored it. A similar resolution then failed in the Senate in September.

For such a resolution to be binding, it would need the force of a law passed by Congress, which the president would likely veto. To overcome that veto, the Democrats would need the support of a two-thirds majority in both the House and the Senate. This would require a significant number of Republicans to cross the aisle.

Exercising oversight

A second option for the Democrats is to launch a series of congressional investigations into the way the war has been conducted. This would likely include public hearings, subpoenas and demands for documents from the Trump administration.

The Democrats may also attempt to impeach senior officials in the Trump administration.

If Hakeem Jeffries, the Democrat tipped to become the next speaker of the House, wants to appease some of the more progressive voices in his party – or the hardline voices on the Iran war or against Trump – Defense Secretary Pete Hegseth could be targeted for impeachment.

But the grounds for such proceedings are unclear at this stage, and even with the Democrats’ new Senate majority, he would be unlikely to be convicted unless a significant number of Republicans crossed the aisle.

More pertinently, congressional investigations are a protracted process, and unlikely to bring the war to a swift end.

The ‘power of the purse’

The more immediate power that Congress has to end the war swiftly is in Article I, Section 9 of the US Constitution, which states:

No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law […]

This is known as the “power of the purse”.

Once the new Congress is sworn in in January, every new dollar that Trump’s Department of War wants to spend needs to be approved by the House and the Senate.

A Democrat-controlled Congress could put a clause into the defence budget, prohibiting funds from being used for hostilities against Iran. Trump could veto this, but this would mean blocking the paycheck for everyone in the military, as well.

The Democrats tried this very approach in 2007, attempting to force a timetable for a US withdrawal from Iraq. Then-President George W. Bush vetoed it, but it became a political football, with both sides accusing the other of leaving US troops unfunded.

The Democrats ultimately backed down due to the growing risk of backlash from voters.

Today, this approach would carry a similar risk. Are the Democrats willing to put their political credibility on the line if the president accuses them of letting American soldiers down? Who blinks first?

Republicans face a reckoning

As the dust settled on Wednesday, Trump himself acknowledged the Iran war had played a role in the Republican Party’s crushing defeat. But he doubled down on the decision, saying he would do it all over again if necessary to prevent Iran from acquiring a nuclear weapon.

Vice President JD Vance was less defensive. In a detailed statement posted to X, Vance bluntly declared the war was the reason the Republicans lost. He added, “any honest conversation about where we go from here must start there”.

Vance has long criticised US military involvement in overseas conflicts, but in his role as vice president has publicly backed Trump’s actions against Iran.

This week’s overwhelming Democratic victory has made it much easier for Vance – and other Republicans – to now break ranks with the president.

The balance of power has shifted

For Trump, bringing the war to an end now would mean humiliation. The US has so far poured almost US$50 billion into a military campaign with few tangible achievements.

On top of that, Iran has learned that the Strait of Hormuz is a chokepoint it can control. The same is true for the Bab al-Mandeb Strait off the coast of Yemen, where the Iran-aligned Houthis have attacked commercial ships.

These costs will outlast the Trump presidency. The war might definitively bring to an end the unipolar global order Washington built after the end of the Cold War. The biggest winner may not be Tehran, but Beijing.