MILWAUKEE - With his party's leaders coalescing around him and his closest rivals acknowledging their faint prospects, Mitt Romney rolls into Tuesday's Wisconsin primary poised to strike another powerful blow in the race for the GOP nomination.

Wisconsin is one of three places to vote Tuesday - along with Maryland and the District of Columbia - but it is here in the Badger State that Romney and his top opponent Rick Santorum have waged the fiercest battles on the campaign trail in the past week.

Santorum once led in the polls here, but more recent surveys show Romney with a double-digit lead. The former Massachusetts governor is likely to win in Maryland and the nation's capital, as well, adding to an already insurmountable lead in his quest to reach the 1,144 delegates required to clinch the nomination.

On Sunday, campaigning near Madison, Romney acknowledged as much, noting that his party's nominee will "probably be me." It was the latest sign of confidence from Romney who had previously predicted he would win here Tuesday.

"It feels better and better," Romney told supporters in Fitchburg over the weekend. "The support for my campaign is growing stronger and stronger. This was an uphill battle for me - if you look back three or four weeks ago - and now we're looking like we're going to win this thing on Tuesday."

"But," he added, "I gotta have you guys get out and vote."

"I got a good boost from the folks in Illinois," he said. "And if I can get that boost also from Wisconsin, I think we'll be on a path that will get me the nomination well before the convention," he added.

In Illinois late last month, Romney cruised to a commanding win, as he has in other key Midwestern states, Ohio and Michigan. His combination of superior organization and a strong war-chest has proved too much to overcome for his rivals.

In the past week, Romney has only bolstered his chances with a string of high-profile endorsements. Former President George H. W. Bush, Florida Sen. Marco Rubio, Wisconsin Sen. Ron Johnson, and Wisconsin Rep. Paul Ryan all threw their support behind Romney and, on Sunday, the Senate's top Republican Mitch McConnell told CNN, "I think he's going to be an excellent candidate and I think the chances are overwhelming that he's going to be our nominee."

Even Romney's rivals sound closer to acknowledging that victory is likely to be his. Newt Gingrich stated last week that "all three" candidates agree they will now start to focus more of their attacks on President Obama, rather than each other.

Santorum even said Sunday that he will "step aside" if Romney clinches a majority of convention delegates and admitted that "we have to win Pennsylvania" on April 24.

However, it was Pennsylvania voters who tossed Santorum out of the Senate after only one term, so he cannot expect much of a home-field advantage there. Even a surprise victory by Santorum would do little to change the fate of the race, especially since the four other states that vote that day - New York, Connecticut, Rhode Island and Delaware - are all likely to go to Romney.

While Santorum tries to make his last stand in Pennsylvania - he is not even hanging around Wisconsin on primary night, instead choosing to hold an event outside Pittsburgh - Romney is already looking ahead towards the general election. In the past week the GOP frontrunner has started to pivot both his organization and his messaging towards the looming showdown with Obama this fall.

At an event in Appleton last Friday, Romney delivered his most "presidential" speech yet - ignoring his GOP rivals and setting his sights squarely on the president.

"He actually thinks he's doing a great job. A historically great job," Romney said. "I mean, how can this be? Is it because the president is so disconnected from what's happening in America that he doesn't grasp the real consequences of his failures? And the answer's easy: the answer is, 'Yes, of course.' This is a president who was not elected on the strength of a compelling record of accomplishment, but by a compelling personality and story."

It was a moment that reflected the momentum that Romney has gained nationwide, including here in Wisconsin.

He is now poised to snag the 42 delegates on offer in the state's winner-take-all primary, bolstered by his strength in the conservative suburbs outside of Milwaukee.

Waukesha County, just to the west of the city, is seen as the key to success in the state - it has been the largest source of Republican votes in state-wide elections. In recent Midwestern primaries, Romney has capitalized on his strength in vote-rich suburbs to override Santorum's advantages in more rural areas. In Illinois, Romney handily won the Chicago area. In Michigan, he won Detroit. In Ohio, Cleveland, Cincinnati and Columbus.

Now Romney will hope to replicate that magic in the Milwaukee area.

Matthew Jaffe is covering the 2012 campaign for ABC News and Univision.