Democrats on Track to Take House; G.O.P. Holds Senate

Among the major races of the night, Senator Joe Donnelly of Indiana and Senator Heidi Heitkamp of North Dakota, two moderate Democrats in increasingly conservative states, were decisively defeated thanks of Republican strength in small towns and rural areas. In Tennessee, Representative Marsha Blackburn, a conservative Republican, was dominating former Gov. Phil Bredesen in the middle and western parts of the state that were once Democratic strongholds. And Senator Ted Cruz overwhelmed Beto O’Rourke, the popular liberal congressman, through much of rural Texas.

“Tremendous success tonight. Thank you to all!” Mr. Trump tweeted late Tuesday night.

But in the House, where Republicans had a 23-seat majority, Democrats captured 17 Republican-held seats through Tuesday night and were ahead in several more districts, with Western states still to be called. Democrats ejected incumbents in the suburbs of Kansas City, Philadelphia, Pittsburgh, Minneapolis, Miami and Washington, D.C.. — winning decisively in moderate districts where Mr. Trump’s racial demagoguery and hard-line nationalism has badly shaken college-educated voters and other parts of the old-school Republican coalition.

Republicans remained deeply anxious through the night about a long list of House seats anchored in the suburbs of the East Coast and the Midwest, with a long night of ballot-counting ahead in blue-tinted districts out West that Hillary Clinton carried two years ago.

“Tremendous success tonight. Thank you to all!”

The two parties each won important governorships. In Michigan, a historic Democratic stronghold that the president carried narrowly in 2016, voters chose Gretchen Whitmer, a former Democratic leader in the State Senate. Illinois voters elected J.B. Pritzker, a Democrat and Hyatt hotel heir, over the embattled governor, Bruce Rauner.

But the party’s hopes for making Andrew Gillum the first black governor of Florida were lost, as the liberal Tallahassee mayor conceded the race to Ron DeSantis, a hard-line former member of Congress aligned with Mr. Trump.