Dr. Abdul El-Sayed, the Democratic Senate nominee in Michigan, apologized to a group of Jewish Democrats on Saturday for a statement he made in March about an attack on a synagogue near Detroit, saying that “nobody deserves to have their pain trampled on.”

Dr. El-Sayed, who is trying to appeal to Jewish Democrats who have expressed deep skepticism about his candidacy, said he should not have included a phrase — “hurt people hurt people” — in a video statement he issued soon after a man drove his truck into the synagogue, injuring a guard. The authorities said the attack, on Temple Israel in West Bloomfield Township, Mich., was a targeted act against Jews.

“I made a mistake,” said Dr. El-Sayed, responding to a question while addressing the Michigan Democratic Jewish Caucus at a party convention in Lansing. “I should have issued a statement, of course condemning it, and it just should have been the full stop.”

Dr. El-Sayed said he had been trying to “offer broader context” but had inadvertently trampled on “the dignity that that fear and that pain should have been afforded.” He added: “If my statement caused pain, I’m sorry. That was not what I intended.”

The authorities said the man who carried out the attack on the synagogue, Ayman Mohamad Ghazali, a naturalized U.S. citizen who was born in Lebanon, had lost family in an Israeli attack in March. In his initial statement, Dr. El-Sayed said there was “never a justification for attacking innocent people” but that he understood that “violence is a cycle” and that “hurt people hurt people.”

On Saturday, Dr. El-Sayed said his attempts to contextualize the attack were inappropriate in its immediate aftermath.

The apology came as Dr. El-Sayed has been under pressure over his links to Hasan Piker, a provocative streamer who has made incendiary comments about Israel. Dr. El-Sayed campaigned with Mr. Piker during the Democratic primary but recently said he had no intention to do so in the lead up to the November general election.

Dr. El-Sayed’s campaign against the Republican nominee, former Representative Mike Rogers, is seen as one in a small group of contests that could determine control of the Senate. Polls show a competitive race.

When Dr. El-Sayed narrowly won the Democratic primary in early August, many Jewish Democrats declined to immediately back him, citing his criticism of Israel — he has called the country’s government “evil” and regularly attacked the American Israel Public Affairs Committee during the primary race — and connections with Mr. Piker.

And Mr. Piker has repeatedly returned to the center of internal debates among Democrats in recent weeks, most recently after he issued what appeared to be an ominous warning to Jewish Americans during an episode of his show a week ago.

Dr. El-Sayed, a forceful critic of the Israeli government, defeated Representative Haley Stevens, a pro-Israel Democrat, to win his party’s nomination. The Democratic Party in Michigan, which has large Jewish and Muslim populations, has been split by debates about Israel, and the issue was at the center of the Senate primary.

The convention where Dr. El-Sayed delivered his apology was itself a source of tension. The state attorney general, Dana Nessel, who is Jewish, said she did not feel safe at the event after Ms. Stevens was booed by party activists at a different convention in the spring.

Before the convention, many Jewish Democrats continued to express concerns about Dr. El-Sayed’s connections to Mr. Piker.

State Representative Noah Arbit, a Democrat from the Detroit suburbs who founded his state party’s Jewish caucus, said Friday in a text message that Dr. El-Sayed should completely “sever ties” with Mr. Piker, describing the streamer as “an illustration of the candidate’s accommodation of unabashedly extremist, authoritarian politics within his coalition.”

Jessica Alexander, chair of the Michigan Democratic Jewish Caucus, said in an interview at the convention on Saturday that she was deeply engaged with the El-Sayed campaign. The campaign, she said, knows “there’s work to do” with the Jewish community. She said that she remained concerned about Mr. Piker but that she did not have concerns about Dr. El-Sayed as a candidate.

Mr. Piker said on his show a week ago that “if Jews in America keep putting this idea out there that they are singularly invested in Israel, eventually someone’s going to come around and take action — not against the State of Israel, mind you, but against American Jews.”

The comment came moments before Mr. Piker assailed Jeremy Moss, a Democratic nominee for the House in Michigan, for declining to endorse Dr. El-Sayed since the primary.

Ms. Moss is Jewish and has said he is concerned about Dr. El-Sayed’s position on Israel. Mr. Moss said in an interview at the convention that Dr. El-Sayed’s apology for the March statement was “genuine,” “credible” and “appreciated” by the caucus.

“We’ve had many meaningful and thoughtful conversations since the primary,” Mr. Moss said. “This was something that got brought up.”

In a public statement responding to Mr. Piker’s remarks, Dr. El-Sayed said that “nobody speaks for this campaign besides me and my campaign spokespeople” and that “all Americans deserve the right to advocate for what they believe without fear of violence.”

“This is particularly true for communities that have been intimidated for their beliefs in the past,” Dr. El-Sayed said in the statement. “My commitment to Jewish safety is the same as my commitment to the safety of my own daughters.”

A drumbeat of Democratic statements denouncing Mr. Piker followed the streamer’s comment. Representative Brad Sherman, a California Democrat, said on social media that Mr. Piker had tried to “encourage and justify violence against American Jews.” Senator Cory Booker, a New Jersey Democrat, wrote on social media that Mr. Piker had “repeatedly and unmistakably” crossed a line that separates “vigorous debate and rhetoric that stokes hatred toward our neighbors.”

Neither Mr. Sherman nor Mr. Booker criticized Dr. El-Sayed directly. But both emphasized they did not believe Mr. Piker should be given a platform. Dr. El-Sayed tried to move past the issue, declaring he was focused on Michigan, not Mr. Piker, who lives in Southern California.

He hit the campaign trail this week with Representative Jamie Raskin, a Maryland Democrat, who is Jewish, and Representative Debbie Dingell, a Michigan Democrat. Mr. Raskin downplayed his party’s divides. Ms. Dingell said she did not “agree with Hasan Piker on a lot of stuff” but implored Democrats not to focus on him.

“Don’t any reporter ask me again about Hasan Piker; it’s not what November is about,” Ms. Dingell said, raising Mr. Piker without prompting in a speech. Republicans, she added, are “trying to divide us.”