When a progressive firm last month polled Black voters, a key Democratic constituency, it found less than half saying their lives had improved under President Biden. A second Democratic-allied firm found that among new voters who backed Mr. Biden in 2020 in competitive states, nearly one-third now thought it would be good if Republicans took over Congress…

The situation feels familiar to Republicans, who lost their House majority in 2018 under a president whose approval rating was well below 50% despite passing a tax cut for most families and corporations. “You’re telling yourself, maybe we can avoid what everyone is predicting,” said Parker Hamilton Poling, a former executive director of the GOP’s main House campaign committee. For Democrats this year, “the political headwinds are probably too strong to overcome, barring some kind of game-changing event.’’…

Democrats so far have the tougher challenge in recruiting candidates and retaining incumbents. With the first state deadlines to file for office coming up in December, only one of the 13 Democratic members of Congress who were defeated in 2020 has agreed to run again, depriving the party so far of candidates with proven fundraising ability and name recognition.