“I meant it when I said the future was going to be made right here in America,” Biden said in a tweeted video with General Motors Co. chair and Chief Executive Officer Mary Barra on Thursday. “Companies like GM and Ford are building more electric vehicles here at home than ever before.”

The tweet didn’t go unobserved by avid Twitter user and Tesla CEO Elon Musk. “Starts with a T. Ends with an A. ESL in the middle,” he replied.

At every opportunity, Biden hails progress Ford and GM have made toward fielding an electric fleet. But his ongoing and obvious snubs of Tesla — a source of mild intrigue within the administration — have sparked increasingly exasperated public reactions from Musk, the world’s wealthiest person and the CEO of both Tesla and SpaceX, which has government contracts with NASA and the U.S. military.

Musk tweeted after the White House event Thursday with Barra and Ford CEO Jim Farley, to which Tesla was not invited, that “Biden is treating the American public like fools.” He added that the president is “a damp sock puppet in human form.” Over the weekend, he egged on fans who started an online petition asking the president to “acknowledge Tesla’s leadership in regards to electric vehicles.”

Read more: Biden’s Praise for GM Overlooks Tesla’s Actual EV Leadership

In 2021, Tesla delivered over 936,000 cars globally. GM sold nearly 480,000 EVs last year, mostly in China. In the U.S., the company had to recall its electric Chevrolet Bolt because of risk of battery fires and sold just 26 EVs in the fourth quarter — 25 Bolts and one electric GMC Hummer pickup truck.

UAW Support

There’s no real mystery behind Biden’s antipathy toward Tesla, according to a person familiar with the president’s thinking. The president has long enjoyed the support of unions in his political campaigns, including the United Auto Workers, and while Tesla employees enjoy generous pay and benefits including equity in the carmaker, Musk is hostile toward unions and company workers aren’t organized.

“Fighting for their right to steal money from workers!” Musk tweeted Nov. 10 in reply to news about an ongoing federal corruption investigation of UAW officials.

Within Tesla, there is a feeling among some executives that all of this is just politics: Biden will never win Texas, where Musk now lives, while Michigan — home to Ford and GM — and UAW support is key to Democratic victories both in upcoming midterm elections and in 2024.

Even some Biden aides say they wish the boss would warm to Musk’s company. “Bums me out as a satisfied Tesla owner,” one said. The White House officials who spoke for this story all asked not to be identified because of the sensitivity of the issue.

Last fall, after a White House event promoting electric vehicles that excluded Tesla, Musk said Biden is “biased” against the company and said his administration “seems to be controlled by unions.”

Read more: Biden Snubs Tesla, Top U.S. Seller of EVs, at Event Touting EVs

Musk has also belittled a key Biden policy: the president’s proposal to reinstate a $7,500-per-car tax credit for EVs and eliminate a cap on the number of vehicles from any one manufacturer that are eligible for the credit. Tesla hit the limit on the original EV tax credit in 2018.

‘Can This Whole Bill’

Biden’s proposal, though, comes with an anti-Tesla twist: consumers would be eligible for an extra $4,500 if they buy an EV assembled by union workers.

“Honestly, I would just can this whole bill,” Musk said of Biden’s Build Back Better legislation in December, shortly before Senator Joe Manchin, a key West Virginia centrist, killed the measure by withdrawing his support.

Read more: Musk Says Biden Administration Is ‘Biased’ Against Tesla

“Tesla has done extraordinary things for electric vehicles and that’s a big part of why the whole industry now knows EVs are the future,” White House spokeswoman Emilie Simons said in a statement to Bloomberg News.

She pointed out that Tesla has “benefited greatly” from EV tax credits in the past. “But, unfortunately, their CEO has suggested an opposition to new EV tax credits,” she said, without using Musk’s name.

Simons said the Thursday event at the White House was for business leaders who support Build Back Better. GM’s Barra recently became chair of the Business Roundtable, a lobbying group in Washington that, like Musk, opposes Build Back Better. But Barra has said she personally supports the measure.

Musk didn’t respond to an email requesting comment for this story. But he later weighed in on Bloomberg’s report with a one-word tweet: “Sigh.”

Read more: Tesla Will Drop Self-Driving Feature That Runs Stop Signs

Tesla, founded in 2003, makes fully electric cars at its factories in California and Shanghai. The company moved its corporate headquarters last year from Palo Alto, California, to Austin, Texas, where it has completed a new factory that’s larger than the Pentagon.

Tesla has about 10,000 workers at its factory in Fremont, California. The UAW, headquartered in Detroit, has made various attempts to organize workers there with little success.

Other purely electric vehicle companies, including Lucid Group Inc. and Amazon-backed Rivian Automotive Inc. are also non-union — and Biden hasn’t said anything about them, either, according to a search of his public remarks at Factba.se. Like Tesla workers, employees at Lucid and Rivian also enjoy stock options as part of their compensation packages.