Mark Dayton (born January 26, 1947) is a Minnesota Democratic-Farmer-Labor Party US Senator from Minnesota who took office in 2001. He was born in Minneapolis, Minnesota. Dayton graduated cum laude Yale University, 1969, where he excelled both academically and athletically, starting in goal for Yale's varsity hockey team. He worked as a teacher in New York City. He was an unsuccessful candidate for the United States Senate in 1982. Dayton had served as a legislative assistant to Senator Walter Mondale. He was Minnesota state auditor, 1991-1995 and elected to the United States Senate in 2000. He defeated Republican incumbent Rod Grams. Dayton's ex-wife, Alida Rockefeller Messinger, is the sister of fellow US Senator Jay Rockefeller making them brothers-in-law.
Dayton, an heir to the Dayton's Department Store fortune, financed his 2000 Senate campaign with $12 million of his own money, but stated he would not do the same for future campaigns.
In October 2004, Dayton closed his Washington office until the November elections, citing reports of a possible terrorist attack. Every other senator chose to keep their office open, and Dayton received national criticism for his move. Already considered a vulnerable incumbent, by the next year his approval ratings had declined by double digits.
On February 9, 2005 he announced that he would not run for re-election, stating, "Everything I've worked for, and everything I believe in, depends upon this Senate seat remaining in the Democratic caucus in 2007. I do not believe that I am the best candidate to lead the DFL Party to victory next year."
On September 22, 2005, the forty-fourth anniversary of the day President John F. Kennedy signed the Peace Corps into law, Dayton became the first U.S. senator to introduce legislation creating a Department of Peace.
In April 2006, Dayton was selected by Time as one of "America's Five Worst Senators." The magazine dubbed him "The Blunderer" for "erratic behavior" such as his closure of his office in 2004.