Rep. Seth Moulton, D-Mass., a third-term congressman who has pushed for a “new generation of leadership” in Washington, declared his candidacy for president today, becoming the 19th candidate to enter the Democratic primary field.

“I’m running because I’m a patriot, because I believe in this country and because I’ve never wanted to sit on the sidelines when it comes to serving it,” Moulton said today on ABC’s “Good Morning America.”

Moulton, 40, garnered attention in November when he helped lead a group of rebellious Democrats who had sought to deny Speaker Nancy Pelosi, D-Calif., the gavel in the new Congress. The effort was unsuccessful and Moulton ultimately voted for Pelosi. His online biography paints him as something of a disrupter, noting that he was “the only Democrat to unseat an incumbent in a primary” in the House of Representatives when he was first elected in 2014.

Moulton, a Harvard-educated Marine veteran, has also focused on recruiting veterans to run for Congress as Democrats, including a handful who campaigned and won in 2018 promising not to back Pelosi.

“We need to restore our moral authority in everything we do. Whether it’s appointing a Cabinet member, negotiating a treaty or signing an executive order, I will always uphold America’s values,” he said in a video announcing his campaign.

“I’m running because we have to beat Donald Trump. And I want us to beat Donald Trump because I love this country.”

During his time in Congress, Moulton, who represents a district in northeastern Massachusetts, has passed bills aimed at improving the way health care is delivered to veterans and making government travel more efficient. Given his background as a veteran, his campaign is likely to concentrate on national security and foreign affairs— areas that have received relatively scant attention from other candidates, who have focused more heavily on domestic issues such as health care and the economy.

By focusing on his military service and his relative youth, Moulton will seek to draw a contrast to President Donald Trump, who is 72 and received several draft deferments during Vietnam.

“I’m going to talk about patriotism, about security, about service,” he said today. “These are issues that for too long Democrats have ceded to Republicans and we’ve got to stop that. Because this is actually where Donald Trump is weakest. We’ve got to take him on on these issues.”

Moulton also has released a plan that outlines a series of changes to the nation’s elections, including automatic voter registration and making Election Day a national holiday. And he has argued for abolishing the filibuster and the Electoral College.

But with so many candidates in the race, Moulton faces a steep uphill climb to the nomination. He is one of four sitting members of the House of Representatives who is running for president. All are seeking to become the first person to be elected president from a seat in the House since James Garfield in 1880.

One of the other House members running, Rep. Tim Ryan of Ohio, is also known for his criticism of Pelosi and for having joined forces with Moulton in the push to replace her as speaker.