What Trump losing power over Congress means for Iran, Ukraine and foreign policy

US President Donald Trump speaks at a midterm campaign rally at the Rock Hill Sports & Event Center in Rock Hill, South Carolina on Oct. 29, 2026.

Kent Nishimura | AFP | Getty Images

With Democrats taking control of both houses of Congress, U.S. President Donald Trump could intensify his focus on foreign policy in his final two years in office, while facing greater scrutiny over the wars in Iran and Ukraine, experts told CNBC.

Democrats will have a Senate majority and won control of the House, giving them greater scope to scrutinize the administration, shape spending and challenge Trump's foreign-policy agenda.

"We are going to see a president that is somewhat constrained on matters of oversight and investigation, but on foreign policy, he does still retain a lot of latitude," Laurel Rapp, director of Chatham House's U.S. and North America Programme, told CNBC's "Squawk Box Europe."

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Rapp said the Iran war was a "major issue" in this election cycle amid soaring fuel prices, food costs, and inflation. The war began when Trump launched joint strikes with Israel on Feb. 28.

Iran war powers

"Republicans don't really have an off-ramp here at this stage. We know the Democrats will seek to take votes in the House and the Senate to constrain the Republicans, to restrain the administration on Iran war powers. But whether that will bind the administration is another matter," Rapp added.

Democrats could use Congress' spending powers to try to restrict funding for the war, she added. Any bill directing Trump to end U.S. involvement would need two-thirds support in both chambers to override a presidential veto.

In a Wednesday note, Berenberg's chief economist, Holger Schmieding, predicted a final round of bombing in Iran, with Trump ultimately striking a deal to reopen the Strait of Hormuz by 2027, as voters feel the sting from high prices and fuel costs.

Mitchell Reiss, a fellow with defense and security think tank RUSI, predicted that Trump would replace Secretary of Defense Pete Hegseth following the results.

"Traditionally, presidents do replace cabinet officials. Certainly, after midterm results like this one, if you remember, George W. Bush replaced Donald Rumsfeld as Secretary of Defense after midterm losses, so that wouldn't be a surprise," Reiss told CNBC on Wednesday.

Trump retains authority

J.C. Lintzenich, visiting senior fellow at the German Marshall Fund, said that the president is not a "lame duck."

"Remember that this election changes the Congress; it does not change the president," Lintzenich told CNBC's "Squawk Box Europe" on Wednesday.

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"The President of the United States still has lots of power, lots of authority. We still have pending action in Iran. We still have an unresolved situation with Russia and Ukraine."

He added that while Congress has changed, foreign policy is still executed by the president and his appointed officials.

"What we'll now see is a little bit more congressional oversight, the application of funding, for example, Ukraine, that's required by statute and law," Lintzenich said.

Lintzenich said the outgoing Congress was "more willing to let the White House slide," but Democratic control of both chambers would mean a more assertive Congress, using its Article I powers over legislation, spending, and oversight to hold the White House more closely to existing law and congressional requirements.

Berenberg's Schmieding warned that Trump could face "more trouble ahead" as Democrats take control of the Senate.

He said Congress was unlikely to fund "an expensive campaign similar to the Iran war, but added that Trump, "as a perennial attention seeker without a consistent long-term strategy," may be "even more eager to pursue dangerous geopolitical adventures."

Russia/Ukraine is the 'tail risk'

Speaking as voting took place on Tuesday, Ukrainian President Volodymyr Zelenskyy said the U.S. midterm elections would "shape the future."

"The world will be watching," he said in Berlin. "Right now, things are deeply uncertain. Many hopes may once again end in disappointment."

Meanwhile, the Kremlin said it hoped the outcome of the midterms would not impact Trump's efforts to broker a peace deal between Ukraine and Russia, Reuters reported, citing local media.

The results could complicate Trump's ability to secure congressional backing or funding for a deal, but they do not prevent him from pressing Kyiv diplomatically. Berenberg's Schmieding said Trump could try to push Ukraine toward a deal favorable to Russia, though he considers that a "tail risk."

Read more of CNBC's Russia-Ukraine coverage:

• Fake nuclear warnings in Ukraine as Moscow, Kyiv report separate cyberattacks on emergency apps
• Russian strikes plunge Ukrainian city into blackout as Zelenskyy warns of more missile attacks
• Trump's Russia diesel deal may offer Putin more than money — and spell trouble for Ukraine
• Zelenskyy accuses Russia of violating Trump’s energy ceasefire as drone attacks continue
• Trump declares ‘energy ceasefire’ between Russia and Ukraine; Zelenskyy is waiting for details
• Ukraine’s surprise robot offensive exposes a vulnerability in Putin’s war machine
• Putin orders army expansion as Zelenskyy warns Russia preparing to deploy 10,000 North Korean troops
• Russia ‘truly’ appreciates U.S. invite to G20 summit — but hasn’t decided if Putin will go
• Zelenskyy says Ukraine ready for ‘energy ceasefire,’ calls for trilateral meeting with Putin, Trump
• Putin floats ‘chance’ at peace with Ukraine as NATO chief warns Russia is becoming ‘increasingly reckless’
• Russia preparing ‘massive strikes’ on Ukraine’s energy sites after deadliest attack of the year
• Russia's economy has defied the skeptics. Cracks are getting harder to hide
• 'Winter is coming’: Ukraine fears its toughest test since Russia’s full-scale invasion

Schmieding said Trump's influence over Republicans could weaken after the midterm defeat, noting that Republicans, including Secretary of State Marco Rubio, are warier of Putin. "That can help to contain the risk of Trump trying to impose an unacceptable deal on Ukraine," he said.

If Trump did pressure Ukraine, Europe would likely increase its support, Schmieding said, but it could not fully replace critical U.S. military and intelligence assistance.

Christel Schaldemose, a vice president of the European Parliament, said the result "could benefit the support for Ukraine" but added: "The EU must continue the course of standing stronger and standing on its own two feet."