Senate Republican Leader Mitch McConnell, R-Ky., isn't endorsing Mitt Romney for president, but says the former Massachusetts governor is on his way to winning the nomination and that it's time for the GOP to focus on the fall campaign.Appearing on CNN's "State of the Union" the Republican leader said Romney would be "an excellent candidate" but that voters don't need him to weigh-in on the race because the Kentucky primary isn't until May. McConnell pivoted and implored the GOP to unite behind one candidate to unseat President Obama in November, indicating the other candidates should drop out."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," he said.From CNN:Romney leads his three opponents—former House Speaker Newt Gingrich, former Pennsylvania Senator Rick Santorum and Congressman Ron Paul—with 571 delegates heading into the Wisconsin, Maryland and District of Columbia primary Tuesday. All three have indicated they are staying in the race despite Romney's lead.He has also lined up a number of key endorsements such as House Budget Committee Chairman Paul Ryan, Florida Senator Marco Rubio and former President George H. W. Bush.