On June 3, 2015, Matthews officially announced that she was a Democratic Party candidate for Maryland's 8th congressional district, where incumbent Chris Van Hollen was relinquishing his House seat in order to run for the United States Senate. On March 16, 2016, the editorial board of The Washington Post endorsed Matthews, writing, "Our preference for Ms. Matthews boils down to our belief that in Congress, she would be more pragmatic and less doctrinaire than the left-leaning State Senator Jamie Raskin, whose passionate liberalism is unsurpassed in Annapolis. Both candidates support gun control, clean energy, campaign finance reform and greater investment in education and health research. Ms. Matthews has greater potential, following the Van Hollen model, to move the ball forward in those areas." On April 26, 2016, Matthews was defeated by Raskin in the Democratic primary.