Mitt Romney and senior members of his vaunted finance team have helped Sen. John McCain raise millions of dollars in recent weeks as the Arizona Republican mulls his options for a running mate.

Some of Romney’s top financiers argue that the former Massachusetts governor’s efforts have helped McCain pull within range of Sen. Barack Obama (D-Ill.) in the presidential money chase.

“The governor and his team are doing everything humanly possible to help McCain,” said Ron Kaufman, one of Romney’s fundraising bundlers.

Kaufman said Romney is already a “game changer” and an important reason “McCain is doing better and better on fundraising every day.”

“By putting him on the ticket, it will energize people to do more,” said Kaufman.

Many Romney donors remain on the sidelines. Only 96 of Romney’s 345 campaign bundlers have given to McCain since Romney suspended his campaign at the end of February, according to an analysis by The Hill.

This may give McCain a strong incentive to pick Romney as his running mate when many political observers believe that Obama could have a major financial advantage over his Republican opponent in the fall.

Obama has raised nearly $296 million through the end of May. McCain has raised just over $122 million.

Romney spent millions of his personal fortune on his own presidential campaign, but campaign finance experts say his wealth could not be spent directly on a McCain-Romney ticket in the general election.

Bob Biersack, a spokesman for the Federal Election Commission (FEC), said that Romney could give only $50,000 of his own money to the campaign because McCain has decided to accept $85 million in public funding for the general election.

Scott Thomas, a former FEC commissioner, said that Romney could donate his millions to Republican-allied 527 or 501(c)4 organizations. But it would be politically difficult for Romney to fund a soft money group to help his own election because McCain has criticized such groups and championed strict campaign finance regulation.

However, Romney has strengthened his case for serving on the GOP ticket by raising millions for McCain.

He has attended multimillion-dollar events in Massachusetts and Michigan. He also attended a big-dollar event in Utah and convened his finance team in Texas the night before McCain held a fundraiser there, said a McCain campaign official.

Some of Romney’s senior fundraisers have taken important roles on McCain’s campaign.

Meg Whitman, one of Romney’s national finance chairwomen, is a McCain campaign co-chairwoman and senior economic adviser. She attended an economic town hall meeting with McCain this week at which the candidate unveiled his economic plan.

John Rakolta Jr., another of Romney’s national finance chairmen, co-chairs McCain’s fundraising team in Michigan. He said a fundraising event Romney attended there raised more than $2 million for McCain in early May.

Michigan had been fertile fundraising ground for Romney this election cycle, owing in large part to Romney’s history in the state. His father, George Romney, served as governor in the 1960s. Democrats won Michigan in the 2000 and 2004 presidential races, but polls show a tight race between Obama and McCain.

Romney and McCain clashed bitterly during the GOP primary, but McCain invited the former governor to his ranch in May along with other vice presidential hopefuls.

Rakolta said Romney’s old finance team would help organize fundraisers for McCain on July 17, July 18 and a few more dates in August. He estimated that about half the money collected at the Michigan events would come from Romney supporters.

McCain has had difficulty attracting the major GOP donors who fueled President Bush’s 2000 and 2004 campaigns. An analysis by The Boston Globe found that only 43 percent of Bush’s biggest fundraisers gave money to McCain’s campaign through the end of May.

Romney’s finance advisers say that the Bush network has become tired and tapped out because of the grueling nature of presidential fundraising, adding that Romney’s fundraising network offers McCain a largely untapped reservoir of donors.

“Those of us who helped Mitt are people who had not done this very much before and, secondly, we were very supportive of Mitt himself,” said Tom Tellefsen, one of Romney’s national finance chairmen. “A lot of people that supported Mitt supported him because of him and weren’t necessarily active [Republican financial] supporters in the past.”

Tellefsen said some of Bush’s biggest fundraisers came out of a fundraising network first built up by former President Reagan and then inherited by Bush’s father, former President George H.W. Bush.

Tellefsen claimed that many of these donors had “been there and done that” and “are at a juncture where they are not motivated to do it anymore.” He noted that Romney had more success raising money from new sources when McCain was having trouble raising money from the traditional Republican network. McCain had spent months courting major Bush donors before his presidential run but still ran out of money months before the Iowa caucuses.

Members of Romney’s old finance team all say that McCain would motivate Romney donors to become much more active if he tapped his former rival.

“About half have decided they will support McCain and the other half is taking a ‘wait and see’ attitude,” said Rakolta, discussing Romney’s financial supporters.

He said many of those waiting on the sidelines have told him, “When Mitt is the VP candidate, I’ll become fully engaged.”