The AP reports:

U.S. Sen. Tom Harkin will not seek re-election in 2014, the Iowa Democrat said Saturday. The 73-year-old Harkin told The Associated Press in an interview, "It's just time to step aside," noting that by the time he would finish a sixth term, he would be 81. Harkin said the move also would allow a new generation of Democrats to seek higher office. The announcement comes as a surprise, considering he had $2.7 million in his campaign war chest and was planning a gala fundraiser in Washington, D.C., next month. Harkin is a leading liberal in the Senate, chairing the health, education, labor and pensions committee and having served as a key salesman of President Barack Obama's 2010 health care bill to the wary left.