The latest polling suggests that Democrats have the edge in the upcoming midterm elections on November 3.
They hope they can flip seats in the House of Representatives and take control of the Senate.
That would make life difficult for Donald Trump in his last two years in office, hampering his chances of passing legislation in Congress.
The state of Iowa has voted for Donald Trump three times, but many voters are angry about rising prices and the war in Iran.
Clive Myrie presents BBC News at Ten reporting by Sarah Smith in Iowa.
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