Bernie Sanders, an independent running for re-election to the United States Senate in Vermont, won all 246 towns in the 2012 General Election. With no Democratic candidate in the contest, Sanders won a solid state-wide victory with 71% of the vote to Republican John MacGovern’s 25%. Chris Ericson of the United States Marijuana party had 2.0% with four other candididates making up the rest (full results). This bested his 2006 result where he received 65% of the vote and won all but two towns (one of the two was a tie).
In recent years, a fairly uniform result across the state in US Senate elections has been relatively common. Republican Jim Jeffords won all towns in 2000, Democrat Patrick Leahy won all but one town in 2004 and all but ten in 2010.