California Representative Eric Swalwell, one of President Trump's most outspoken critics in Congress, announced he is seeking the presidential nomination in what is shaping up to be the largest Democratic primary field in U.S. history.

The 38-year-old San Francisco area lawmaker announced his presidential campaign during an appearance on "The Late Night Show with Stephen Colbert" airing Monday night on CBS.

"I've already done a lot, but I can do more," he said in a clip released by the show. "I've been in Congress for six years. I've defended our country from the Intelligence Committee while Democracy has been on the ropes."

Swalwell enters a crowded race for president with more than a dozen candidates seeking to capture the Democratic nomination and thwart Mr. Trump's reelection bid next year. To date, 17 other Democrats have declared their candidacy for president or launched presidential exploratory committees, including Sens. Bernie Sanders, Kirsten Gillibrand, Kamala Harris, Cory Booker and Elizabeth Warren; Ohio Rep. Tim Ryan; Hawaii Rep. Tulsi Gabbard; Texas Rep. Beto O'Rourke; and South Bend, Indiana, Mayor Pete Buttigieg.