Note: We originally posted this item on April 5. We're resurfacing it now, in light of Sen. Lisa Murkowski's Wednesday announcement that she supports gay marriage. With the Supreme Court expected to rule soon on cases involving gay marriage, the issue is front and center once again. So, it's worth revisiting which Senate Republican might be next to follow in the footsteps of Murkowski and Sens. Rob Portman (R-Ohio) and Mark Kirk (R-Ill.). We've taken Murkowski off the list, and reached out to the offices of the remaining senators on it. We will update with any change in position.

On the Democratic side, there are currently three senators who have not come out in support of gay marriage: Mark Pryor of Arkansas, Mary Landrieu of Louisiana, and Joe Manchin of West Virginia. Since we first posted this item, Sen. Tim Johnson (D-S.D.) announced his support for gay marriage. We've updated the post to reflect that. 

Original post:

Earlier this week, we took a look at the few remaining Senate Democratic holdouts (the list has shrunk by three since it was published) who had yet to express support for gay marriage. What about Senate Republicans? Only two have come out in favor of same-sex marriage. Who might the next one be?

Below, we offer our best educated guesses based upon two overarching factors: The 2010 vote to end the military’s “Don’t Ask, Don’t Tell” policy that prevented gays from serving openly, and the political tilt of the states represented by Senate Republicans. We take a closer look at GOP senators who voted for repeal of DADT, and/or come from states carried twice by President Obama. The list — which is presented in order of most to least likely — is meant to start the conversation, not as a definitive rundown set in stone. Agree/disagree with any names? As always, the comments section awaits.

1) Sen. Susan Collins (R-Maine): Like Murkowski, Collins is a moderate who voted to repeal DADT. She also comes from a state Obama carried twice. Collins says the issue of marriage should be dealt with at the state level. "I've always felt that domestic relations, including marriage, should be dealt with at the state level," she recently told the Associated Press. “My philosophy has been to stay out of state issues." That’s not an endorsement of same-sex marriage, but it doesn’t mean she won’t offer one in the future. Also, Collins's former Republican Senate colleague, Olympia Snowe, declared her support for same-sex marriage Friday.

2) Sen. Richard Burr (R-N.C.): Burr unexpectedly voted to repeal DADT, after first backing an effort to filibuster the measure. He explained at the time that he didn’t think the timing was right for repeal, but that after the filibuster had was stymied, he decided to support it. "This is, I think, a policy that generationally is right,” he told the Hill newspaper of his feelings about repeal at the time.  He recently told local news outlet WRAL that his "personal opinion" is that marriage  is "between a man and a woman, but my role is not to influence what people believe in the state I live in or what the state does that I live in." It's worth noting that Burr's colleague in the Senate, Democrat Kay Hagan, recently announced support for same-sex marriage.

3) Sen. Kelly Ayotte (R-N.H.): Ayotte comes from a state that Obama won twice and gay marriage is legal. “Ultimately I do think this is a matter for the states and states should decide how to define marriage. New Hampshire’s already made that decision and I respect the decision," she recently told New Hampshire Public Radio. Ayotte hasn't shown any signs that she is moving toward supporting gay marriage, but it's worth keeping an eye on lawmakers from New Hampshire, a state with a history of pols with independent streaks.

4) Sen. Pat Toomey (R-Pa.): Toomey wasn’t in the Senate for the DADT vote, but he expressed support for repeal as senator-elect. Like many of the names on this list, he comes from a state carried twice by Obama. “Senator Toomey believes that the tradition of marriage is sacred and is best defined as between a man and a woman. He does realize that there are many Americans who feel strongly about this issue and support marriage for same-sex couples. The input of Pennsylvanians is therefore valued when Congress reviews legislation addressing same-sex marriage,” said a Toomey spokesperson.

5) Sen. Ron Johnson (R-Wis.): Johnson also comes from a state Obama carried twice, and his Senate colleague from Wisconsin is Tammy Baldwin, the nation’s first openly gay senator. “People have strong and deeply-held opinions about marriage and family because they are central to our society. I believe that we should continue to leave it up to the people – acting through the states – to set guidelines. The federal government should not override the choices of any one community in an attempt to impose a national standard, but should respect the rights of the people and the states,” Johnson said in a statement.

There are three other Republican senators hailing from states that Obama won twice who have not declared support for gay marriage. While they are also worth keeping an eye on, there is less reason to believe they will support same-sex marriage in the near future.

Sen. Marco Rubio (R-Fla.) is one, but it’s hard to imagine him shifting on this issue since he’s viewed as a potential presidential contender and would have to appeal to conservatives if he runs. He recently said in a speech at the Conservative Political Action Conference, "just because I believe that states should have the right to define marriage in a traditional way does not make me a bigot."

Sen. Dean Heller (R-Nev.) is another one, but he voted against the repeal of DADT in the House. “Senator Heller supports traditional marriage, and believes this is an issue that should be decided on a state level,” said spokesman Chandler Smith.

Sen. Chuck Grassley (R-Iowa) is a third Senate Republican from a state Obama won twice. Grassley voted against ending DADT and hasn’t changed his view about marriage so far. “Senator Grassley opposes same-sex marriage. His position has not changed,” said spokeswoman Beth Levine.

Of the eight Republican senators who voted to end DADT, only four are still in the Senate: Burr, Collins, Kirk and Murkowski.

One other GOP senator to keep an eye on is the chamber's newest member: Jeff Chiesa of New Jersey. One the one hand, coming from a blue state, Chiesa is worth watching as someone who might come out in support of gay marriage. But it's also worth noting that Chiesa's record has appeared to irk gay marriage advocates, which would seem to work against the prospect of him publicly supporting it. Chiesa's stance on the issue has been somewhat vague. His office did not immediately respond to a request for clarity.

Meanwhile, over on the Democratic side, there are three senators who have not endorsed same-sex marriage: Mark Pryor of Arkansas, Mary Landrieu of Louisiana,  and Joe Manchin of West Virginia. Pryor and Landrieu face tough reelection bids in 2014. Manchin does not face reelection until 2018.

Updated at 2:44 p.m.