There were a number of signs in recent days that more elected Republican officials were getting in line behind Mitt Romney in recent days, with the latest endorsement coming from a 2010 Tea Party favorite, Sen. Ron Johnson of Wisconsin.

“It is time to end this,” Johnson said in an appearance on NBC's Meet the Press on Sunday, arguing for Romney's main opponents to exit stage right.

"Let's show that this is the time to bring this process to an end so we can focus our attention on retiring President Obama," Johnson added.

Also notable was that Romney and Senate GOP Leader Mitch McConnell have named Sen. Johnson to put together a GOP agenda that Romney can share with Congressional Republicans.

In other words, the big guns are moving into the camp of Mitt Romney - not Rick Santorum.

Sen. Johnson - who was elected in 2010 with strong Tea Party backing - joined fellow Badger State lawmaker Rep. Paul Ryan (R-WI) in backing Romney's campaign for the White House, which seems to be on the verge of a triple win Tuesday in primaries in Maryland, Washington, D.C. and Wisconsin.

With Romney heavily favored in Maryland and D.C., Wisconsin has become the battleground in recent days, with Romney and Santorum totally focused on the Badger State, and then will continue today as well.

The last four polls have Romney ahead of Santorum by ten, seven, five and eight points, with Newt Gingrich and Ron Paul not even a factor, struggling to get into double digits.

Over the weekend, Santorum vowed to go on in the GOP race even if he loses all three primaries on Tuesday - but realistically, his path forward is getting more and more difficult.

The only other primaries in April are in Pennsylvania, New York, Delaware, Connecticut and Rhode Island. Pennsylvania is Santorum's home state - but the others would seem to be prime turf for Romney.

And every delegate that he chalks up this month makes it that much more difficult for Santorum to stop Romney's drive for the GOP nomination.