Democrats Battle for Senate Control as They Push to Expand House Majority

“Tonight, Kentuckians said, ‘We’re not finished yet,’” Mr. McConnell told supporters in Louisville. “Kentucky wants more of the policies that built the best economy in our nation’s modern history — not socialism.”

In the fight for the House, Democrats were more clearly on the offensive, bolstered by a stunning fund-raising advantage, Republican recruitment failures and Mr. Trump’s eroding support in America’s cities and suburbs. Two years after gaining 41 seats to reclaim the majority, Democrats were trying to push into suburban districts that Republicans have not lost in decades around St. Louis, Indianapolis, Atlanta, Phoenix, Omaha and even once ruby-red parts of Texas. Strategists in both parties said a second blue wave could wash out 10 to 20 Republicans, and a less successful night might yield Democrats only a handful of new seats.

“Tonight, House Democrats are poised to further strengthen our majority, the biggest, most diverse, most dynamic, women-led House majority in history,” Speaker Nancy Pelosi of California said on Tuesday before the polls closed.

“There is nothing normal about what’s in the White House,” she added, “but normally, this would be the start of healing.”

Anything but a dramatic upset would be a disappointment for Republicans, who began the cycle hoping to grab onto Mr. Trump’s coattails and a booming economy to wrest back the 30 or so districts he won in 2016 that Democrats claimed two years later. Those hopes were dashed by the pandemic, which has left the economy in tatters and the nation counting more than 230,000 deaths to date, and Democratic candidates in many of the districts they once hoped to reclaim were poised to walk to a second term, with signs of consolidating Democratic support that could keep the districts out of Republican reach for years.

Still, Republicans found some unexpected bright spots. With Mr. Trump making significant inroads among Cuban-Americans in Miami, Representative Debbie Mucarsel-Powell, a first-term Democrat, was edged out by Carlos Gimenez, the Miami mayor, and Representative Donna E. Shalala lost to Maria Elvira Salazar, a former television anchor.