Embattled Facebook CEO Mark Zuckerberg will draw the anger and frustration of both Republican and Democratic lawmakers Tuesday, when he sits for a joint Senate hearing to field questions about data security, his effort to police “fake news” that appears on his giant media site, and foreign government meddling in the 2016 presidential election.

Zuckerberg seemed to acknowledge the seriousness of the questions facing his company by donning a suit as he made an initial round of meetings Monday, a far cry from the casual T-shirt he often wears.