Twitter owner Elon Musk has proposed hosting Twitter Spaces interviews with political candidates of all stripes, reflecting the billionaire's supposed commitment to ideological neutrality and to promoting Twitter as a true "public square."

So far, however, Musk appears to be more interested in platforming candidates that align with his own views rather than those who might challenge them. On Monday, Musk is set to share an audio chatroom with Robert Kennedy Jr., the anti-vaccine activist and Democratic candidate for president.

The decision to host Kennedy again highlights, for the second time in as many weeks, Musk's unique potential to shape public opinion through a combination of his own personal celebrity and his private control of a social media megaphone. But this time, it also deepens doubts about Musk's claims to open-mindedness — and his willingness to use Twitter as anything other than a tool for his own activism.

Musk, who built much of his early reputation as an entrepreneur on a concern for ensuring humanity's survival, has opposed the Covid-19 vaccine and spent much of the pandemic railing against Anthony Fauci, the government's former top infectious disease expert. Musk has claimed as recently as January that he is "pro vaccines in general" but that they risk doing more harm than good "if administered to the whole population."

Medical experts widely agree that the broad application of vaccines helps prevent the spread of disease not only by making it less likely for an individual to get sick, but also by creating herd immunity at the societal level. In other words, part of the purpose of vaccines is to administer them as universally as possible so that even if one person falls ill, the infection cannot find other suitable hosts nearby.

For years, Kennedy has pushed back on that consensus, including by invoking Nazi Germany in an anti-vaccine speech in Washington last year. Instagram shut down his account in 2021 for "repeatedly sharing debunked claims about the coronavirus or vaccines," though the company announced Sunday it has restored Kennedy's account because he is now running for office. Instagram's parent, Meta, has also banned accounts belonging to Kennedy's anti-vaccine advocacy group.

Kennedy has also attacked the closing of churches, social distancing and government track-and-trace surveillance. At the start of the pandemic, churches were closed and social distancing was enforced across the country to contain the spread of coronavirus, while the government used methods to track cases. (Musk, for his part, also objected to state lockdown orders earlier in the pandemic.)

It's unclear if Musk has reached out to other candidates. Twitter did not immediately respond to a request for comment.

According to a CNN poll published last month, 60% of Democratic and Democratic-leaning voters say they back President Joe Biden for the top of next year's Democratic ticket, 20% favor Kennedy and 8% back Williamson. Another 8% say they would support an unnamed "someone else."

With the national profile and visibility that comes with running for high office, Kennedy's anti-vaccine ideology and vocal stances against prior Covid policies were already primed to become a topic of the 2024 presidential race. But by putting Kennedy center stage on Twitter, Musk appears poised to promote these views further to his millions of followers.

Musk took a similar tack in sharing a stage with Florida Republican Gov. Ron DeSantis, who announced his White House bid with Musk during a Twitter Spaces event last month plagued by technical glitches. Musk declined to endorse a candidate but has previously tweeted that he would support DeSantis if he ran for president.

As Twitter's owner, Musk has shared conspiracy theories and welcomed extreme voices back to the platform who had been suspended for violating Twitter's rules in the past. He has also laid off more than 80% of Twitter's staff, including many who had previously been responsible for content moderation.

All of that, combined now with his direct association with Kennedy, could have significant ramifications both for Twitter as a platform and for Musk's credibility.

DeSantis at least has the plausible distinction of being a top challenger to former President Donald Trump. But as a marginal candidate who espouses debunked medical claims, Kennedy and his appearance with Musk could further cement the perception that Twitter actively mainstreams extremism.

That could be the very thing that drives away more moderate candidates from accepting Musk's "invitation" to appear alongside him.