In a statement provided Thursday by Washington United for Marriage, Evans said that approving Referendum 74 "just seems right and reflects the fundamental value of fairness that we treasure here in Washington."
Evans was governor of Washington for three terms, serving from 1965 until 1977. He served in the U.S. Senate from 1983 until 1989.
R-74 asks voters to either approve or reject the law allowing gay marriage that was passed earlier this year by the Legislature and signed by Democratic Gov. Chris Gregoire. The law has not yet taken effect, and remains on hold pending Tuesday's election.