On Thursday night it appeared that feuding Democrats in Michigan had made peace on the eve of a crucial Senate election. But on Friday morning, tensions returned with a vengeance. Rep. Haley Stevens of Michigan had said she would campaign this weekend with Dr. Abdul El-Sayed, the Democratic Senate candidate and her former primary rival, apparently overcoming a series of recent public criticisms she leveled at him. Less than 24 hours later, I had another message. In a statement promoting her plan to join Dr. El-Sayed on the campaign trail, she said she hoped Dr. El-Sayed would apologize for comments he had made about Israel and that she anticipated he would repudiate what she described as an anti-Semitic ad by an outside group. He also asked him to remove a campaign ad that featured Tucker Carlson. “Abdul promises to make money out of politics,” Stevens said in the statement. “You can start by taking Israel out of its explanation of everything Michigan can’t afford.” The statement was the latest twist in an unusual and tense dance between Dr. El-Sayed and Ms. Stevens that has involved a widening circle of Democrats, including Representatives Debbie Dingell and James E. Clyburn of South Carolina, one of the highest-ranking African Americans in Congress. The friction has added turbulence to the final week of a race that could determine control of the Senate, raising concerns in the party about divisions that could prove costly as Election Day approaches. El-Sayed’s campaign did not immediately respond to requests for comment. Stevens, a centrist who lost to Dr. El-Sayed by less than a percentage point in a bitter August primary, has not been seen publicly with Dr. El-Sayed in the final stretch of the race, despite promising over the summer to campaign with him. Instead, Ms. Stevens, a staunch supporter of Israel, has made a series of cable news appearances in which she has questioned his outreach to black and Jewish voters. Her fiancé, a Jewish Democrat, said Wednesday that he was endorsing Dr. El-Sayed’s opponent, Mike Rogers, the Republican Senate candidate. On the same day, Ms Stevens said she would not campaign with Dr El-Sayed ahead of Tuesday’s election. Wednesday’s events left Ms. Dingell, leader of the party’s Michigan congressional delegation, frustrated. Then, he said, he called Dr. El-Sayed and Ms. Stevens and told them they should campaign alongside Mr. Clyburn, the South Carolina Democratic power broker. On Thursday, a joint appearance with Dr. El-Sayed, Ms. Stevens and Mr. Clyburn was scheduled for Sunday at a black church in Detroit. Ms. Stevens described the meeting as a “souls to the polls” event. “I’m the one who made this happen,” Ms Dingell said, adding that the problem had been that Dr El-Sayed and Ms Stevens “weren’t talking”. When Ms. Dingell pressed her, “They said, OK,” she recalled. “It was that simple,” he said. But the dynamic between Dr. El-Sayed and Ms. Stevens is not simple. And even when Ms. Stevens agreed to join Dr. El-Sayed, she suggested that her appearance was the product of an upcoming grant from Dr. El-Sayed, and sought to secure another. In his statement, he said he understood Dr. El-Sayed would repudiate the announcement by the outside group, a left-wing political action committee called Rebellion PAC, adding that he had heard about those plans through party leaders and the media. “That’s why I accepted Congressman Clyburn’s invitation to appear with Abdul,” Ms. Stevens said. The ad, placed in a grocery store, suggests that American aid to Israel is the source of rising prices in the United States. It shows a shopper telling a man not to buy eggs because “we have to save those $7 to kill Palestinians.” Stevens argued in her statement that the ad “did not invent its argument,” but advanced one she said Dr. El-Sayed had been making during the election campaign. “So I hope he apologizes,” he said. Cenk Uygur, the founder of Rebellion PAC, argued that Ms. Stevens had a “bizarre” interpretation of the ad and that it was critical of the Israeli government, not American Jews. But he said he wouldn’t mind if Dr. El-Sayed denounced the commercial. “He is running a campaign,” Mr. Uygur said. “I’m running a PAC. He can say whatever he wants. I’m okay with that. We don’t talk to each other.” In her statement, Ms. Stevens also called on Dr. El-Sayed to pull a campaign ad featuring Mr. Carlson and other conservative figures influencing the race. Carlson, who has frequently espoused conspiracy theories and said white supremacy is “not a real problem” in the United States, has spoken out against Rogers and defended El-Sayed’s criticism of American foreign policy. Ms. Stevens said Dr. El-Sayed should withdraw the ad out of “respect for the black community in Michigan.” It was unclear whether Ms. Stevens and Dr. El-Sayed had any direct communication. Clyburn, who endorsed Ms. Stevens in the primary, said he would not discuss planning for Sunday’s event, but acknowledged that he had spoken with Ms. Dingell. “I don’t know who else he talked to,” he said. “But she did talk to me.” Clyburn’s arrival comes as El-Sayed is trying to overcome tension between black and Arab American voters in the Detroit area. He also faces skepticism from some Jewish Democrats, who object to his fierce criticism of Israel. In late August, he apologized to a group of Jewish Democrats for using a phrase in March – “hurt people, hurt people” – after an attack on a synagogue near Detroit. “No one deserves to have their pain trampled on,” he said in his apology. The primary contest between Dr. El-Sayed and Ms. Stevens was personal and focused largely on Israel. Dr. El-Sayed, highlighting Ms. Stevens’ endorsement by the American Israel Public Affairs Committee, once said the group had chosen to back “America’s least capable candidate.” Ms. Stevens said Dr. El-Sayed wanted to blame his “problems on American Jews.” After Dr. El-Sayed won, Ms. Stevens quickly endorsed him and they appeared together at a unity breakfast. He said the party had a “good candidacy” and was united. But her fiancé, Jason Turkish, said Wednesday that he remained disappointed months later that Dr. El-Sayed had not appeared with Ms. Stevens at a news conference the day after the primary, and had instead teamed up with Mallory McMorrow, another candidate who dropped out of the race in July and finished a distant third.