WASHINGTON (AP) — Elon Musk and Donald Trump share bestride-the-colossus egos, an incessant desire to be the center of attention and a platform to showcase their eccentricities and erraticism.

Both the Tesla CEO and the former president have used that platform, Twitter, as a sword and a shield — a soapbox to rouse the passions (and tap the pocketbooks) of tens of millions of followers and repulse the other side.

Trump weaponized Twitter before he was banned after the Jan. 6, 2021, attack on the U.S. Capitol. Musk was a persistent Twitter poster, taunting stock market regulators and railing aga...