Democrats set to use congressional spending powers to challenge Trump on Iran

Democrats are preparing to challenge Donald Trump’s foreign policy through congressional spending decisions and investigations after winning control of both houses in Tuesday’s US elections. The Iran war and international tariffs are seen as important contributors to the inflationary pressures that helped drive voters away from Republicans.

The Republican defeat has also opened a dispute within the president’s party over the war. Vice-President JD Vance blamed the election result on Trump’s decision to attack Iran, writing on X: “The reason we lost is the war.” Donald Trump Jr endorsed Vance’s assessment. Trump acknowledged that the conflict had raised gasoline prices but defended continuing it, arguing that Iran must be prevented from acquiring a nuclear weapon.

Although Democrats will have majorities in the House and Senate, they will lack the votes needed to overcome a presidential veto. That makes control over federal spending a particularly important source of influence. Ryan Crocker, a former career diplomat and diplomatic fellow at the Middle East Institute, said the Pentagon’s request for a substantial increase in funding for the Iran war was likely to become the first major confrontation.

An opportunity to demand concessions will come in December, during Congress’s lame duck session, when the continuing resolution financing the government expires. Democrats could also seek restrictions on the Iran campaign or presidential authority as conditions for advancing the National Defense Authorization Act. The Senate version would authorise approximately $1.15tn in national defense spending for 2027.

One progressive foreign policy thinktank has proposed adding provisions to the continuing resolution that would bar congressional funds from supporting wars in Iran, Yemen, Lebanon and Gaza. Crocker cautioned that a government shutdown could carry political costs. He said Democrats should recognise that voters’ anger reflected opposition to Trump’s conduct and policies as much as support for their own party.

Earlier attempts to limit Trump’s foreign policy illustrate the obstacles ahead. In 2019, Congress passed a bipartisan War Powers Act resolution seeking to end US support for Saudi Arabia’s war in Yemen, but Trump vetoed it. Jennifer Hendrixson White, a visiting scholar at the Carnegie Endowment for International Peace, said investigations into the Iran war or defense contracts involving Trump-linked companies could embarrass or pressure the president, while questioning whether they would produce substantive restrictions.

Relations with Israel are also facing scrutiny across party lines. In his response to the election, Vance urged Republicans to end the Iran war, address living costs and inflation, put America first and change the US relationship with Israel. Amit Segal, a political analyst close to the Netanyahu administration, described the result as a major challenge for Israel’s position in Washington.

Michigan Democrat Abdul El-Sayed, who will become the first sitting Muslim senator next year, welcomed Trump’s decision to end military aid to Israel at the close of 2026. El-Sayed also called for halting weapons sales to Israel, citing their use in actions he described as genocide and apartheid.