Some national security concerns

Per the Washington Post:

• He blurted out a highly classified piece of information to Russian leadersthat risked jeopardizing a key foreign policy alliance.
• He has engaged in multiple highly secretive face-to-face meetings with Russian President Vladimir Putin where even top national security officials were in the dark.
• He kept Michael Flynn on as national security adviser for weeks despite warnings that Flynn could be susceptible to blackmail because he had lied to the White House.
• He turned a dining room at Mar-a-Lago into an open-air situation room, strategizing about a North Korean missile launch with Japanese Prime Minister Shinzo Abe.
• There have been reports that Trump has disregarded advice from security experts about his cellphone use and even that he has pressed forward with an unsecured phone we know the Russians and Chinese can listen in on.
• Multiple top White House aides have reportedly used private email to discuss White House matters, both potentially flouting records laws and posing unnecessary security threats.