By Michael Martinez, CNN
(CNN) -- The Illinois Senate will vote Thursday -- Valentine's Day -- on whether to legalize same-sex marriage.
Because Democrats have supermajority control of the General Assembly, the measure is expected to be approved. After the Senate vote, the measure would be considered by the House.
Gov. Pat Quinn, a Democrat, has indicated he would sign the bill.
If it is approved, Illinois would be the 10th state, plus the District of Columbia, to legalize same-sex marriage, according to Lambda Legal, a gay rights organization.
Three other states are considering similar legalization, said Camilla Taylor, marriage project director for Lambda Legal. A bill has passed the Rhode Island House and has been sent to the Senate. A proposal has been introduced in the Hawaii legislature and another is expected in Delaware, Taylor said.