This is the week John McCain takes a measure of what the Republican nomination is worth. The Arizona senator, less than a week removed from having secured enough delegates to become his party’s presidential standard-bearer, sets out on a nationwide fundraising drive aimed at restocking his campaign kitty.

Starting Monday in St. Louis, and continuing Tuesday in New York, Wednesday in Boston and other unannounced cities through Friday, McCain will reach out to the GOP faithful. His aim is the funding necessary to help him match up against the record-shattering totals posted by Democrats Barack Obama and Hillary Rodham Clinton.

They continue to battle for their party’s nomination, fueled by unprecedented monthly and even daily fundraising sums.

“We can see the great job that our opponents have done in fundraising. We’ve got a lot of work to do,” McCain said.

An invitation to McCain’s event Wednesday night at the Taj Boston hotel is fairly typical: $2,300 donations — the maximum allowable each primary and general election campaign — are required for a private reception with McCain. A half-hour later, the tab drops to $1,000 per person for a more widely accessible general reception.

Among those slated to attend are the head of a major biotechnology company, Boston Scientific co-founder Peter Nicholas, as well as former acting Massachusetts Gov. Jane Swift, a longtime McCain backer, and former Gov. Paul Cellucci, who previously supported former New York Mayor Rudy Giuliani.

There was conflicting word about whether former Massachusetts Gov. Mitt Romney, who joined Giuliani in battling McCain for the Republican nomination, would attend the event.

The challenge confronting McCain is stark. During the current election cycle, Obama and Clinton have not only outraised him, but far exceed him in cash on hand.

Obama, a senator from Illinois, has raised $141 million, with $25 million cash on hand as of Jan. 31. Clinton, a senator from New York and former first lady, has raised $138 million and had $29 million cash on hand.

By contrast, McCain has raised $55 million and had $5.2 million cash on hand at the end of January.

McCain and Obama have bickered over their prior commitment over a general election spending cap should they emerge as their respective party’s nominee, but that debate was rendered moot last week by Clinton’s reemergence as a challenger to Obama following big-ticket wins in the Ohio and Texas primaries.

Obama and Clinton are expected to battle through April and possibly to their party’s August convention, yet McCain must raise enough money to support his organization and remain in the public spotlight without benefit of a nomination contest.

One booster will be President Bush, who endorsed his fellow Republican last week and pledged to help McCain however he can, especially on the fundraising front.