Who is Democratic presidential candidate Bernie Sanders?
Vermont Senator Bernie Sanders is Hillary Clinton's closest rival for the Democratic presidential nomination, even surpassing her in some polls. So who is he?
Former First Lady and Secretary of State Hillary Clinton may have once been the presumed Democratic nominee for president, but 74-year-old Vermont Senator Bernie Sanders has been steadily gaining on her in the polls.
In the last quarter of 2015, he raised $33 million to Mrs Clinton's $37 million, but without the aid of a political action committee and mostly in small amounts from individuals.
Some say Mr Sanders emerged as the star of some of the Democratic debates so far with his call for a "political revolution" and a taming of the billionaire class. He gets a consistent amount of buzz post-debate on social media, including the most new Facebook followers and more hits on Google than Mrs Clinton.
So, who is he and what does the "Democratic socialist" candidate stand for?
Mr Sanders was born in Brooklyn, New York, to Jewish parents. He once said his humble upbringing in a tiny apartment made him class-conscious at an early age.
He attended the University of Chicago, and in the 1960s and 1970s participated in antiwar and civil rights activism, like the 1963 March on Washington.
He applied for conscientious objector status during the Vietnam War, though he was too old to be drafted by the time his application was rejected.
Mr Sanders entered politics in 1971 when he ran for Vermont Senate as a Liberty Union candidate, a party with antiwar and socialist roots. He lost that race as well as several subsequent campaigns to become governor.
His first major political success came when he was elected mayor of Burlington, Vermont, in 1980, beating the six-term incumbent by 10 votes. He served four terms.
It was during this time that he met and married his current wife, Jane O'Meara Driscoll, the former president of Burlington College once described as a "key adviser" in his political career. Combined, they have four children from previous relationships.
He was first elected to the US House in 1990, the first independent to do so in 40 years. He served there until he ran for and won a seat in the Senate in 2007. During the campaign, a younger Barack Obama stumped for him.
Since he first arrived in Washington, Mr Sanders criticised Republican and Democratic politicians as being beholden to wealthy donors and industries - for this he was sometimes dismissed as a gadfly. He is the longest-serving independent in congressional history.
In 2010, he famously stood and spoke for eight-and-a-half hours to attempt to block the extension of Bush-era tax policies that Mr Sanders said benefited the rich and worsened the nation's income gap.
He became the chair of the Senate Veterans Affairs committee in 2013 and helped negotiate bipartisan solutions when former soldiers complained of dangerously delayed and inadequate care around the country. He was a staunch opponent of the Iraq War.
He is fond of praising the social policies of Nordic countries, like universal health care and paid leave for new parents. He espouses making institutions of higher learning free.
Mr Sanders has been attacked for his voting record on gun control, including his opposition to various forms of the Brady Bill, which required background checks and waiting periods for gun purchasers. Mr Sanders defends his record saying it reflects the priorities of his Vermont constituents.