“He’s on the ballot, regardless of whether his name is there or not,” Mr. Strickland said of the president. Mr. Trump added that the shift in the political climate between 2016 and 2018 was like “the difference between heaven and hell.”
Mr. Trump has appeared to turn his attention in the last few days away from the effort to keep control of the House, and toward shoring up Republicans in coveted Senate races. He has focused predominantly on electrifying the right rather than soothing some of the swing voters who backed him over Hillary Clinton two years ago.
In the final weeks of campaigning, Mr. Trump has delivered slashing attacks on immigration, railing against birthright citizenship, linking immigration without evidence to violent crime and amplifying debunked conspiracy theories about a migrant caravan in Latin America. In a possible portent of how he might react to electoral defeat, Mr. Trump lashed out at House Speaker Paul D. Ryan on Twitter after Mr. Ryan criticized his dubious proposal to void the constitutional guarantee of citizenship to anyone born on American soil.
Mr. Trump’s approach may resonate in several of the states with the closest Senate races, though it has the potential to backfire in several diverse states where Republican-held seats are at risk, including Nevada, Arizona and Texas.
“It turns off independent voters,” said Senator Chris Van Hollen, a Maryland Democrat and head of the Democratic Senate campaign arm, arguing that such states offered his party “a narrow path” to a majority.
Christine Matthews, a Republican pollster, said the Democratic message, focused on health care, was “more relevant” to most voters than what Mr. Trump was offering them in his final argument. Likening the election to a tug of war, Ms. Matthews said the president was trying to energize his predominantly white and male base even as moderate women recoil from him.
“On one end, you’ve got white college-educated women pulling hard, pulling back from what we’re seeing,” Ms. Matthews said. “On the other side of the rope, you’ve got non-college-educated men pulling hard in the other direction.”