Sen. Tim Johnson, D-S.D., announced Monday that he will support same-sex marriage. His decision leaves only three Democratic holdouts on the issue in the Senate. 

"After lengthy consideration, my views have evolved sufficiently to support marriage equality legislation," Johnson said in a written statement on his website. "This position doesn't require any religious denomination to alter any of its tenets; it simply forbids government from discrimination regarding who can marry whom." 

As more and more Democratic senators announced their support for same-sex marriage over the past few months, Johnson became one of fewer and fewer holdouts in his caucus. Talking Points Memo notes that Johnson recently announced he would not seek re-election next year and should suffer no political backlash from his position. 

The Associated Press reports that in the past, Johnson has stated he was personally opposed to same-sex marriage, but would not support a nationwide ban. His home state of South Dakota has twice passed laws against same-sex marriage, first banning same-sex marriage in 1996 and announcing that it will not recognize same-sex marriages from other states in 2000. 

Now, Johnson has joined the ranks of 50 Democratic senators that have publicly backed same-sex marriage. The only holdouts in the party are Sens. Joe Manchin of West Virginia, Mark Pryor of Arkansas and Mary Landrieu of Louisiana. Last week, Manchin announced that he would continue to support the Defense of Marriage Act. 

“I believe that a marriage is a union between one man and one woman," Manchin told Talking Points Memo last week. "My beliefs are guided by my faith, and I support the Defense of Marriage Act.”

Pryor has announced that he is “undecided” on the issue in an interview with Arkansas’ KFSM

In addition to Johnson and the other 49 Democratic senators publicly supporting same-sex marriage, the Associated Press notes that two Republican senators have announced their support as well: Sens. Mark Kirk of Illinois and Rob Portman of Ohio.