ANNAPOLIS, Md. (AP) — The Maryland Senate is expected this week to debate and vote on a measure to legalize gay marriage as supporters prepare to resist amendments that they say could kill the measure.

Republican leaders asked that discussion of the bill be postponed until Thursday. The measure is expected to pass and would make Maryland the eighth state to legalize gay marriage.

Senate President Thomas V. Mike Miller said the Senate could meet into Thursday night to consider the bill, which barely passed the House of Delegates last week. Debate could continue Friday before a final vote is taken, the Democrat said.

Last year the Senate passed a similar measure by 25 to 21.

Opponents have offered an amendment to change the bill’s effective date. They also say they have asked Attorney General Doug Gansler for feedback on the constitutionality of amendments added to the House version.

Letters regarding the amendments, which would delay the bill’s effective date from October to January 2013 and keep the law from going into effect until any litigation related to a potential voters’ referendum on the measure is processed, were issued from the attorney general’s office to House members last week.

The letters confirmed that delaying the effective date would only ensure that a referendum on the bill could be adequately executed and that the other amendment is constitutionally sound.

Sen. C. Anthony Muse, D-Prince George’s, who voted against the bill last year, said he will also offer an amendment during debate.

“This is such a sensitive issue,” Muse said. “It’s an issue that I think deserves the kind of time and debate that we’ll need in order to deal with this in an adequate fashion.”

Sen. Jamie Raskin, who will shepherd the bill on the floor, said those who want to see the bill pass should resist amendments because it would send the measure back to the House where gathering enough support for altered legislation would be difficult.

“I think that we all know that any effort to amend the bill at this point is essentially to kill the bill,” the Montgomery County Democrat said. “It may look like a placebo, but it is a poison pill.”

Advocates say they are confident they have not lost any votes.

“I don’t anticipate a single vote has changed, but if it has, fine,” said Miller, who opposes the legislation. “That’s up to the body.”

Opponents vow to petition the bill to referendum if it passes the Senate, which would put the measure to voters in November.

They will need to collect at least 55,726 valid signatures of Maryland voters to put it on the ballot and can begin collecting names as soon as the bill passes both chambers.

(Copyright 2012 by The Associated Press. All Rights Reserved.)