Bernie Sanders, a self-described Democratic Socialist, is trying for the second time to win the Democratic nomination. “Our campaign is about transforming our country and creating a government based on the principles of economic, social, racial and environmental justice,” he says.

Accomplishments: Sanders served as the mayor of Burlington, Vermont, the state’s largest city, for eight years before he won his first seat in the House of Representatives in 1990, running as an independent after Democrats did not field a candidate of their own. He then won seven more House campaigns in Vermont and three for the Senate.

Foreign policy: Sanders was one of a minority of senators to vote against going to war with Iraq in 2002. During his time in Congress, he has been an outspoken critic of international trade agreements and used his 2016 presidential campaign to push the Democratic Party to oppose the Trans-Pacific Partnership (TPP), which was negotiated under the Obama administration. Recently, he has worked with a bipartisan group of senators to pass a war powers resolution to end America’s involvement in the Saudi Arabia coalition bombing of Yemen.

What sets him apart: Sanders is the only candidate to have run in the 2016 election. While he lost the Democratic nomination to Hillary Clinton, he won 13 million votes during the primary season and consistently won the votes of Democrats under age 30. He enters the race with the biggest social media following and mailing list of any of the Democratic candidates, and has a proven ability to raise large sums of money from small-dollar donors. If elected, Sanders, at 78, would be the oldest nominee ever selected by a major political party.

Platform: Sanders has long advocated an ambitious liberal agenda, starting with his signature universal health care plan called “Medicare-for-All” that has now been adopted by many of his Democratic challengers. He has argued that many in the country have been left behind as Wall Street and other elites prospered and has advocated for free college tuition and higher taxes on the rich.