Without issuing an official endorsement, Senate Minority Leader Mitch McConnell joined the chorus this morning, saying it’s time for Republicans to accept Mitt Romney as the probable nominee and to turn their attention to the fall campaign.

“It’s absolutely apparent that it’s in the best interests of our party at this particular point to get behind the person who is obviously going to be our nominee and to begin to make the case against the president of the United States,” McConnell told CNN Chief Political Correspondent Candy Crowley.

Asked why he has not thrown his support behind Romney in the form of an endorsement, McConnell said voters in the upcoming contests in Wisconsin, Maryland and the District of Columbia do not need his advice.

“Most of the members of the Senate Republican Conference are either supporting him, or they have the view that I do, that it’s time to turn our attention to the fall campaign,” he said. …

“I think he will be an outstanding nominee,” McConnell said. “I think he can win the election.”

Mitt Romney has a commanding lead in the delegate count (568 to Rick Santorum’s 273), and he’s poised to win primaries in Wisconsin, Maryland and Washington D.C. tomorrow. The best chance of any of the other candidates to secure the nomination is to thwart him from securing a majority of delegates before the Republican National Convention in August, but even Romney’s competitors seem to doubt that possibility. Newt Gingrich, for example, has signaled that he plans to train his attacks on Barack Obama once again, a possible signal that he fully expects Mitt Romney to be the nominee.

Whether Romney will be as competitive in the general as McConnell claims remains to be seen. A new Gallup/USA Today poll shows Obama leading Romney in 12 key swing states by a solid nine points. Just a month ago, Romney held a two-point edge in those same states. Women under 50 are largely responsible for the boost to Obama, who can claim the support of more than 60 percent of them.

The Fix’s Chris Cillizza and Aaron Blake ask the key questions:

There’s little debate that Romney is as low (or close to it) as he has ever been in a matchup against Obama — whether nationally or in swing states. What’s less clear is a) how much of Romney’s current struggles are directly attributable to him, and b) whether his poll numbers are a moment in time or have the potential to be a longer-term problem.

On both questions, I think Republicans have reason to be hopeful. Nothing inherently “Romney” has alienated women. In fact, I’d argue that it’s not that Romney has lost the support of women so much as it is that Obama has gained that support. How? He’s made repeated references to Malia and Sasha. He has appropriated in-the-news figures like Sandra Fluke and Trayvon Martin as his own children. At the very same time that he’s waging a war on women’s fertility, he’s appealing to their maternal instincts with his parental rhetoric. Brilliant. Meanwhile, Romney and the Republicans remain cold and distant as they discuss issues that matter primarily for the ways they touch on people’s personal, private lives. Voter reactions to candidates — especially as captured in polls — are visceral, emotional. Romney has yet to tap into the power of the heart, but, if and when he manages to make the case that Republicans stand for the freedom that leads to prosperous individuals and flourishing families, he’ll be able to win women voters over again.