Where are the most expensive midterm races and who is funding them?

On Tuesday, voters across the United States will head to the polls to cast a ballot in the 2026 midterm elections. The race is expected to serve as a referendum on Republican President Donald Trump’s job performance so far, at the halfway mark of his second term. Maintaining the Republican majority in both chambers of Congress will be key for the success of Trump’s legislative agenda in his final two years. But control of the US Congress could hinge on a handful of closely contested Senate and House of Representatives races nationwide.