A wave of local and regional Teamsters union branches in battleground states rushed to endorse Vice President Kamala Harris after the national Teamsters union declared that it would not endorse a presidential candidate for the first time in nearly three decades.

Teamsters regional councils — representing hundreds of thousands of members and retirees — in Michigan, Wisconsin, Nevada and western Pennsylvania — endorsed Harris hours after Teamsters President Sean O’Brien revealed Wednesday that the union would withhold its endorsement, saying, “neither major candidate was able to make serious commitments to our union.”

Separately, powerful local Teamsters unions in Philadelphia; New York City; Long Beach, Calif.; and Miami — as well as the union’s National Black Caucus and a group of retirees — have endorsed Harris and urged members to vote for her.

“Both Vice President Kamala Harris and Governor Tim Walz have consistently demonstrated their dedication to championing the labor movement,” Kevin D. Moore, president of Teamsters Joint Council 43, which represents some 245,000 members and retirees in Michigan, wrote in a letter to Harris on Wednesday, announcing the endorsement.

He urged “all Teamsters members … to lend their support to this outstanding campaign.”

The Teamsters endorsements have drawn intense scrutiny because the union has a strong presence in battleground states — and unions have an unusualability to mobilize their memberships.

Some Democratic strategists say the outpouring of local endorsements for Harris could be more important in influencing how Teamsters turn out to vote than the national union’s decision to abstain. Local unions typically mobilize members directly through workplace conversations, door-knocking, leafleting and mailers.

“Union members don’t follow endorsements. They follow programs of political action, which are based in their workplaces and local unions,” said Larry Cohen, former president of the Communications Workers of America union and a Democratic operative working on voter turnout.

Still, the national union’s lack of an endorsement marks a blow to the Harris campaign, some strategists said, in light of the Biden administration’s many achievements for unions. It also gives former president Donald Trump and his allies new ammunition to tout union members — who traditionally lean Democrat — as among his supporters.

At a rally in Uniondale, N.Y., on Wednesday night, Trump thanked O’Brien and Teamsters members across the country. “Because this was a surprise,” he said. “It’s automatic they endorse the Democrats.”

Elon Musk took to his social media platform X on Wednesday to share a post from a right-wing account with polling results of Teamsters membership that showed Trump leading Harris by a significant margin. That post said, “Without support from union members, Democrats are toast. This is major.”

The Teamsters released results from two internal surveys of members that they say show rank-and-file members strongly favored a Trump endorsement over one for Harris. The Teamsters reported the periods during which the polls were conducted, whether they were conducted by phone or online, and the percentages that supported Trump and Harris. But the Teamsters did not disclose how participants were selected for the surveys, the number of people who completed them, whether the samples were weighted by demographics, or the exact questions they asked.

The Teamsters said these surveys influenced their decision to not endorse. However, a chorus of union leaders and political strategists questioned them and their methodologies, as no details were released. The Washington Post has also inquired about the methodologies.

A national Fox News poll of registered voters conducted in mid-September found Harris with 53 percent support to Trump’s 47 percent among union households, within the poll’s margin of error. In 2020, Joe Biden led Trump with voters in union households by 56 to 40 percent, according to media exit polls.

Steve Rosenthal, a Democratic political strategist in the labor movement for decades, said the Teamsters’ non-endorsement “allows Trump to say, ‘Union members support me. It’s just union leaders that don’t,’ which isn’t the case. You see lots of polls that bear that out.”

The Teamsters have endorsed the Democratic ticket in every presidential election since 1996, when they did not endorse a candidate. The union had closer ties to the GOP decades ago, endorsing presidents Richard M. Nixon, Ronald Reagan and George H.W. Bush.

The Teamsters’ non-endorsement also reflects a major chasm within the union. Some labor experts say O’Brien has adopted a more bipartisan approach under pressure to consider the membership’s diverse political leanings. He ascended to the union’s top office in 2021 after running as a reform candidate who promised more member involvement in union decision-making. O’Brien is also aware that many rank-and-file Teamsters are Trump supporters, experts say.

The union met behind closed doors with Harris on Monday, and earlier this year with President Biden.

O’Brien met with Trump at his Mar-a-Lago estate in January and held a roundtable with the former president at the union’s headquarters. He also addressed the Republican National Convention in July, becoming the first union president to do so — outraging Democrats, who felt betrayed in light of the Biden-Harris administration’s efforts to champion labor.

The budding relationship with Trump also spurred backlash from liberal Teamsters leadership and many rank-and-file members. After the conventions, a growing cohort of Teamsters local unions began issuing endorsements for Harris, and in some cases condemning O’Brien for not endorsing her.

As of Thursday, at least eight regional councils, covering active Teamsters members in some 14 states, as well as 10 union locals, had endorsed Harris. The regional councils alone represent more than 500,000 Teamsters members.

No regional or local Teamsters organizations have endorsed Trump.

Scott Clement and Hannah Knowles contributed to this report.