In North Carolina, Nida Allam, the Sanders-backed candidate, lost to Valerie Foushee, a state legislator, in an open congressional race. Ms. Foushee’s campaign was supported by nearly $3.5 million in spending from two pro-Israel groups and a super PAC linked to a cryptocurrency billionaire. Super PAC spending for Ms. Allam was $370,000.
Maya Handa, Ms. Allam’s campaign manager, said Mr. Sanders’s megaphone — he did robocalls, sent a fund-raising email to his giant list and held a virtual event — brought invaluable attention to the outside money flooding in the race.
The message broke through to some voters. In Hillsborough, Elese Stutts, 44, a bookseller, had been planning to vote for Ms. Foushee. However, on Election Day, Ms. Stutts said, she was turned off after learning about the origin of the super PAC money that had helped Ms. Foushee’s campaign.
Ms. Foushee ultimately won the Democratic primary for a district that includes several major universities, including Duke and the University of North Carolina at Chapel Hill, and where Mr. Sanders registered 83 percent favorability among Democratic primary voters in the Allam campaign’s polling.
Mr. Sanders has sparred with pro-Israel groups over the years, including during his 2020 presidential run, when a group called the Democratic Majority for Israel PAC spent money to attack him when he emerged as a front-runner early in the primary season.
And when one of Mr. Sanders’s national co-chairs, Nina Turner, ran for Congress in a special election in 2021 and again in 2022, that group and the AIPAC-aligned super PAC both spent heavily to defeat her.
Understand the 2022 Midterm Elections
Why are these midterms so important? This year’s races could tip the balance of power in Congress to Republicans, hobbling President Biden’s agenda for the second half of his term. They will also test former President Donald J. Trump’s role as a G.O.P. kingmaker. Here’s what to know:
“I understand Senator Sanders’s grudge against us,” said Mark Mellman, the president of Democratic Majority for Israel PAC. “We helped prevent him from winning Iowa and the presidential nomination. Then we helped stop his campaign chair from winning a House race in Cleveland. Honestly, I wouldn’t be happy with us either, if I were him.”