Voters struggling with high prices and angry over an unpopular war with Iran will decide whether to drastically shift power in Washington in midterm elections Tuesday that will serve as a referendum on President Donald Trump's second term.

Democrats were cautiously optimistic about their prospects as they watched Republicans spend the campaign's final stretch pumping tens of millions of dollars into states and districts that Trump won handily just two years ago.

They are betting that discontent over Trump's failure to deliver on his promise to tackle rising costs and perceptions that he has been more focused on gilding the nation's capital than their pain at the pump will depress Republican turnout and drive their own voters to the polls.