A Romney supporter waves a campaign sign at an April rally in Tempe, AZ. Romney took that state in the February primary. (Gage Skidmore/Flickr)

Former Massachusetts Governor Mitt Romney is the presumed nominee at this point. Ryan Williams, a spokesman for Romney's campaign, said today will mark the unofficial beginning of the bid for the White House. "We're bringing the nomination process to a close," Williams said, "and will kick off the general election."

CBS News reported Romney will still fall short of the 1,144 delegates necessary for a nomination even if he takes the 219 up for grabs Tuesday. He now has 688, and will likely need another month to meet the requirement. But as Romney returns to New Hampshire—where he started his campaign 10 months ago—insiders say the candidate is undeterred.

From CBS:

"We're getting ready to enter Phase Two," said New Hampshire senior adviser Jim Merrill. The significance of such a transition is not lost on Merrill, who has been working the ground for Romney in the Granite State for years. "It feels right to come back to New Hampshire where we started this thing."

A big part of that Phase Two will include settling on a running mate. According to The Washington Post, a recent campaign stop featuring a special guest has added fuel to the rumors that Florida Senator Marco Rubio may become his sidekick for the November election.

Romney's aide Beth Myers has been assigned the task of narrowing down the list of viable options.

From The Post:

“Beth Myers has begun to put together a number of the names and criteria and so forth that would be associated with that process,” Romney told reporters in a joint question-and- answer session with Rubio yesterday outside Philadelphia. “But we really haven’t had a discussion yet of putting together a list or evaluating various candidates.”

Romney said he and Myers have begun looking for the people -- including those well-versed in examining financial records -- who will help scrub potential candidates’ backgrounds for any impropriety, political liability or other problems.

“We’re looking at various people, resources to help with that process, accounting staff and so forth, to take a look at tax returns and things of that nature,” Romney said. “It’s just at the very early stages.”

Also on the short list: Florida Gov. Jeb Bush, Louisiana Gov. Bobby Jindal, Ohio Sen. Rob Portman, Rep. Paul Ryan of Wisconsin and Virginia Gov. Bob McDonnell. 

The Post reported an April 19 poll by Quinnipiac University showed New Jersey Gov. Chris Christie highlighted as the best-known and best-liked of the potential VP candidates. Personality and likability are among the many intangible factors under consideration in the search for a suitable running mate.

Christie has said the VP spot is not necessarily his goal, but according to The Post, the governor added "it would be 'extraordinarily arrogant' of him not to listen to Romney if he were to ask him to join the Republican ticket. If 'Mitt Romney calls and wants to discuss it with me, I will sit down and talk with Governor Romney about it.'"

Meanwhile, Rubio is staying mum on the rumors, telling reporters in Pennsylvania Monday, "I don't want to talk about it."

GOP voters may have several months of this kind of speculation to look forward to; VP nominees usually make their grand entrances during the party's national convention, scheduled for Aug. 27 this year.

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