First Amendment experts say Mr. Trump’s lawsuits, based on an unproven legal theory, lack merit. But more could be on the way.

President Donald Trump is stepping up his war with the media in his second term, shaking up the White House briefing room, blasting his favorite adversaries, and even trying to cut off government funding streams for certain news outlets.

Armed with multimillion-dollar lawsuits and regulatory threats, Donald Trump is taking his long-standing battle with the US media to a new level –- targeting the finances of organizations already struggling in an increasingly tough commercial climate.