Now that Rick Santorum has withdrawn from the Republican nomination race, Mitt Romney’s challenge will be to unify the party quickly.  He got plenty of help last night from Hilary Rosen, who attacked Ann Romney for being a stay-at-home mom and created a massive reaction among conservatives rallying to defend her.  Today, two key conservative groups announced endorsements for Romney in a move that may help stoke momentum for the all-but-certain nominee.  First, the conservative women’s group and fundraising organization Susan B. Anthony List came out with a strong message of support:

The Susan B. Anthony List, which endorsed Santorum and campaigned feverishly on his behalf by taking a campaign tour bus across the country, is now supporting the former Massachusetts governor for the GOP nomination to take on pro-abortion President Barack Obama.

“Now is the time to unite behind Governor Romney in order to defeat the most ideologically pro-abortion president in our nation’s history,” said Marjorie Dannenfelser, president of SBA List. “The SBA List is proud to endorse Governor Romney and plans to spend $10 to $12 million in senate and presidential battleground states mobilizing pro-life voters to ensure victory.”

“Women deserve a president who truly respects our views on an issue so central to womanhood,” continued Dannenfelser. “A President Romney will be that man. If there was murkiness during the last election over Barack Obama’s extreme abortion position, absolute clarity exists now – and his abortion position is rejected by women young and old.”

“The difference between Governor Romney and President Obama couldn’t be clearer, which is why our Board of Directors voted unanimously to get behind him,” said Jane Abraham, Chairman of the SBA List Board of Directors. “It is the responsibility of all pro-life voters to now unite behind Governor Romney. Together we can put a pro-life leader in the White House.”

The National Right to Life PAC also announced their endorsement of Romney, and drew stark contrasts between the Republican nominee and the Democratic incumbent:

Determined to secure a pro-life victory in the November election, which will decide the fate of unborn children for decades to come, the National Right to Life Committee (NRLC), the federation of 50 state right-to-life affiliates and more than 3,000 local chapters, today endorsed Mitt Romney for President of the United States.

“On pro-life issues, Mitt Romney and Barack Obama provide a stark contrast. As the country’s most pro-abortion president, Barack Obama has pursued a radical pro-abortion agenda,” said Carol Tobias, president of National Right to Life. “It is now time for pro-life Americans to unite behind Mitt Romney. For the sake of unborn children, the disabled, and the elderly, we must win.”

Mitt Romney has taken a strong pro-life position and is committed to implementing policies to protect the unborn, the medically dependent and disabled, and the elderly.  Romney opposes abortion and has called the Supreme Court’s Roe v. Wade decision, “a big mistake.” Romney has expressed his support of the Hyde Amendment, which prohibits the use of federal funds to pay for abortion. …

In comparison, since taking office in January 2009, President Obama has been an outspoken advocate for abortion and has unceasingly worked to expand funding of and access to abortion.  He rescinded the Mexico City Policy, threatened to veto the entire federal spending bill – forcing a government shutdown – rather than accept a provision cutting funding to Planned Parenthood, the nation’s largest abortion provider. Obama also threatened to veto the Protect Life Act, which would repeal the abortion-expanding provisions of his health care law, and the No Taxpayer Funding for Abortion Act, which would permanently prohibit any federal program from funding elective abortion.

Romney needs these kinds of endorsements, and as early as he can get them.  SBA List had endorsed Santorum, which makes their quick shift to Romney all the more significant.  The NRLC had refrained from endorsing any specific candidate, claiming that all four Republicans would represent an improvement over Obama, and in fact scolded its Georgia affiliate in February for singling out Santorum and Gingrich.

In that context, this endorsement looks significant indeed.  Gingrich, after all, continues to insist that he’s still in the race — and this morning insisted that he wouldn’t work for Romney even if Gingrich was offered a job, although he’d be happy to advise him:

Newt Gingrich said on Thursday he would “probably not” accept a Cabinet position under a Mitt Romney administration but would be happy to advise the former Massachusetts governor on policy.

Asked the question in an interview with local radio station WILM at the Hollywood Diner, Gingrich, one of three contenders left in the race for the GOP presidential nomination, said he wouldn’t be interested in joining likely nominee Romney’s Cabinet, but added—“not because I am opposed to Mitt.”

“Look, if the choice does end up being Romney versus [President] Obama, I can be very, very enthusiastic for Romney; that is a huge choice,” the former House speaker said. “But I had a very good life doing a lot of fun things: I’m a grandfather, I’ve got two grandchildren I want to spend time with, Callista has got me into being a really bad golfer. I would like to move up from bad to mediocre.”

The quick announcement of both organizations of their support for Romney might be intended not just to boost Romney, but to tell the other Republicans that it’s time to consider other options for their futures.  So far, it doesn’t appear that Gingrich is getting the message.