WASHINGTON (AP) -- After a three-month struggle, Mitt Romney edged into the mop-up phase of the race for the Republican presidential nomination on Wednesday, buoyed by Newt Gingrich's decision to scale back his campaign to the vanishing point and Rick Santorum's statement that he would take the No. 2 spot on the party ticket in the fall.
Romney campaigned by phone for support in next week's Wisconsin primary while he shuttled from California to Texas on a fundraising trip, praising Gov. Scott Walker, for "trying to rein in the excesses that have permeated the public services union." The governor faces a recall election in June after winning passage of state legislation vehemently opposed by organized labor.
Romney aides eagerly spread the word that former President George H.W. Bush would bestow a formal endorsement on Thursday, although they declined to say whether former President George W. Bush has been asked for a public show of support.
Seven months before Election Day, there was ample evidence of a preparation gap with the Democrats.
A spokesman at the Republican National Committee said the party had recently opened campaign offices in three states expected to be battlegrounds this fall and would soon do the same in seven more.
By contrast, Obama's re-election campaign has 18 offices in Florida, nine in Michigan, a dozen in Ohio, 13 in Pennsylvania and seven in Nevada, according to officials. While Romney was campaigning in last winter's Iowa caucuses, Democrats claimed to have made 350,000 calls to voters as part of an early organizational effort.
And while Romney is still raising money for the second half of the primary campaign, Obama recently reported $84 million in the bank for the general election.
Not that Romney was leaving the primary wars behind. He and Restore Our Future, a super PAC that supports him, were outspending Santorum and his allies on television by a margin of more than 4-1, with an attack-heavy diet of television ads.
In addition, Romney's campaign attacked Santorum in a recorded message called into thousands of homes.
"I was shocked to find out that Rick Santorum repeatedly supported big labor and joined with liberal Democrats in voting against right-to-work legislation during his time in Washington," it says. "He even opposed the hiring of permanent replacements for striking workers. When it comes to big labor, Rick Santorum's record of opposing right-to-work legislation and standing with union bosses speaks for itself."
Santorum is campaigning across the state as an ally of Walker.
"I'm excited to stand here with Gov. Walker. Not only should he not be recalled, he should be re-elected," Santorum said in LaCrosse, Wis. "When Gov. Walker ran and your lieutenant governor ran, they didn't run as they would be moderates. They said the problems in Wisconsin were serious."
There was no let-up in Santorum's criticism of Romney, whom he said is "completely out of sync with America" and "uniquely disqualified" to lead the party against President Barack Obama.
But after absorbing defeats in a string of industrial states in the past month -- Michigan, Ohio and Illinois -- he said of Wisconsin: "I think we'll do well here. The question is how well."
Washington, D.C., and Maryland also hold primaries next week, but Santorum is not on the ballot in the first contest, and he has little if any campaign presence in the second. There are 95 delegates at stake in the three contests.
For the first time, Santorum on Monday seemed to acknowledge publicly that his quest for the presidential nomination may end in failure.
Asked in an interview with Christian Broadcasting Network whether he would consider running as Romney's vice presidential ticketmate, he said: "Of course. I'll do whatever is necessary to help our country."
Gingrich took an even more obvious step toward the campaign exit, although he struck a defiant note one day after announcing that he would support Romney if the front-runner can win a majority of delegates by the time the primary season ends in June.
"For some reason everybody in the establishment is chanting that Santorum and I should quit. Romney has to earn this. It's not going to be given to him," he said. At the same time, his aides were explaining that he had pushed out his campaign manager, trimmed his staff by one-third and would cut back on personal campaign time in primary and caucus states in favor of contacting unpledged delegates.
The Associated Press tally showed Romney with 568 delegates and on a pace to reach the required 1,144 in the remaining primary and caucus states. Santorum has 273, and Gingrich 135.
Romney has reaped several endorsements in the past week, since trouncing Santorum in the Illinois primary.
Bush has long been in his corner, but aides to Romney said Thursday's event was something different, a formal endorsement from the ex-president and his wife, Barbara.
Bush's son was generally viewed as the more conservative president of the two, but his popularity waned among Republicans as well as Democrats and independents when the economy cratered in 2008.
Associated Press writers Thomas Beaumont in Iowa and Steve Peoples in Washington contributed to this report.