Democrats winning in all key states

Democratic candidates for the Senate in Arizona, Nevada, Pennsylvania and Wisconsin lead their Republican rivals and are running well ahead of President Biden in key states where he continues to struggle, according to polls The battleground surveys of registered voters indicate that the president’s difficulties against former President Donald J. Trump may not be enough to sink other Democrats, especially Senate incumbents who are facing less-well-known Republicans. Ticket-splitters are not abundant — about 10 percent of Trump voters back the Democratic candidate for Senate in the four states, while about 5 percent of Biden supporters back the Republican. But those voters are enough to give Democrats a chance at holding the Senate, where they currently hold a one-seat majority. To maintain control, the Democrats would have to sweep every competitive Senate seat and win the White House. In Pennsylvania, Senator Bob Casey, a Democrat, has the support of 46 percent of voters, against the 41 percent who say they back his Republican challenger, the wealthy finance executive David McCormick, although Mr. Trump holds a slender advantage in a head-to-head race with Mr. Biden, 47 percent to 44 percent. In Wisconsin, the Democratic incumbent, Senator Tammy Baldwin, holds a wider, 49-percent-to-40 percent lead over the Republican banker Eric Hovde. Mr. Biden is up slightly against Mr. Trump, 47 percent to 45 percent. In Nevada, where Mr. Biden is struggling the most, Senator Jacky Rosen, a Democrat, narrowly leads her Republican challenger, Sam Brown, a wounded combat veteran, 40 percent to 38 percent, with 23 percent of registered voters undecided. In Arizona, the one battleground state polled with an open Senate seat, Representative Ruben Gallego, a Phoenix-area Democrat, leads Kari Lake, the Republican former news anchor who is closely allied with Mr. Trump, 45 percent to 41 percent, with 14 percent undecided. Mr. Trump leads Mr. Biden in Arizona, 49 percent to 42 percent. The contrasting results underscore the power of incumbency, and how it appears to be nullified in the case of a former president challenging a sitting president. Voter after voter expressed comfort with the sitting Senate Democrat, and an almost complete lack of knowledge about the Republican challengers.