On May 26, 2015, Independent U.S. Senator Bernie Sanders officially announced his run as a presidential candidate for the Democratic nomination, after an informal announcement in April that year, and speculation since early 2014. Sanders had served as Mayor of Burlington, Vermont (1981–1989), as Vermont's sole U.S. Representative (1991–2007), and as Vermont's junior Senator (2007–present). Bernie Sanders is currently seen as the biggest rival to Hillary Clinton, backed up by a strong grassroots campaign and social media following. His campaign picked up attention and mass support. However, in recent poll numbers, Clinton is leading Saunders nationally by 12.7 percent.