Elon Musk is all in for Donald Trump’s campaign.

The billionaire endorsed Mr. Trump shortly after the attempt on his life last month. He’s helped form a political action committee to financially support the Trump campaign, and he’s bashed the former president’s political rivals online.

And on Monday, Mr. Musk planned to host a live appearance with Mr. Trump on X, his social media platform.

Mr. Musk, now more than ever, is using X to promote his personal political views. With more than 193 million followers, his account is the biggest on the platform and Mr. Musk has filled it with praise for the former president. He also accelerated attacks on President Biden over the past year, and he’s recently stepped up criticism of Vice President Kamala Harris.

By endorsing a presidential candidate, Mr. Musk has broken with other heads of social media companies, who typically try to avoid public endorsements.

Mr. Musk hasn’t always been so outspoken about his political opinions. SpaceX, his rocket company, receives contracts from the federal government, and Mr. Musk had incentive not to burn relationships with either political party. Tesla has also benefited from tax credits for electric vehicles and other government incentives. But as SpaceX and Tesla have become more dominant in their respective industries, Mr. Musk has faced less pressure to appease political leaders.

Mr. Musk’s use of X as a political megaphone has led to speculation that he is stifling accounts that promote Democratic causes. When an official account for the Harris campaign was caught in a spam filter and was temporarily blocked from receiving new followers, users blamed Mr. Musk for the glitch.

The European Union recently placed restrictions on social media companies under the Digital Services Act that require them to remove misinformation from their platforms. It has opened an inquiry into whether X has violated the act.

Thierry Breton, the European Commissioner, sent Mr. Musk a letter on Monday warning him that he was responsible for moderating misinformation during the livestream with Mr. Trump.

“We are monitoring the potential risks in the E.U. associated with the dissemination of content that may incite violence, hate and racism in conjunction with major political — or societal — events around the world, including debates and interviews in the context of elections,” Mr. Breton wrote.

Linda Yaccarino, X’s chief executive, wrote on the platform in response that the letter was “an unprecedented attempt to stretch a law intended to apply in Europe to political activities in the U.S.” She also pushed back on the idea that X is biased toward any political party, agreeing with an employee who called the platform a “swing state.”

Mr. Musk promoted the upcoming interview. “This is unscripted with no limits on subject matter, so should be highly entertaining!” Mr. Musk posted on Sunday evening.

Ryan Mac contributed reporting.