Obama, who is expected to report raising between $30 million and $35 million in March, plans to spend a money-packed afternoon and evening Sunday at the northern California homes of four different financial backers.
Clinton, whose March total was expected to be about $20 million, was attending a fundraiser Wednesday in Silicon Valley, followed by three events Thursday in San Francisco, Pasadena and Los Angeles.
Most of the events are for donors giving the $2,300 maximum allowed by law.
The attention to money comes as both campaigns ramp up spending heading into the April 22 primary in Pennsylvania. Obama, who has raised more money than Clinton, is already outspending her even as she launched a new ad in the state Wednesday criticizing Republican John McCain's economic policies.
Obama raised a record $55 million in February; Clinton raised $34.5 million. Their March fundraising reports won't be filed with the government until April 20; the totals cited are based on estimates from advisers.
Clinton aides said Wednesday that they anticipate Obama will outspend her by 2-to-1 in Pennsylvania. In the first round of campaign ads, Obama spent about $2 million to Clinton's $450,000, according to data compiled by TNS Media Intelligence/Campaign Media Analysis Group, which tracks political ads.
Obama, an Illinois senator, trails Clinton in public opinion polls in the state.
"We don't expect to match Senator Obama ad for ad," Clinton communications director Howard Wolfson told reporters during a conference call Wednesday. "We will have significant resources to compete and be resourceful, but we know that Senator Obama will outspend us significantly."
Clinton has been at a financial disadvantage this year. She began March with $11.5 million to spend in the primary compared to $30.5 million for Obama. Moreover, Clinton owed $8.7 million to several campaign vendors at the end of February. A spot check by The Associated Press of several vendors found many were paid last month, after the March 4 primaries in Ohio and Texas. The cost of those two contests, together with efforts to reduce campaign debt, have kept fundraising a priority for her campaign.
And though the New York senator trails Obama in delegates needed for the nomination, Clinton advisers and fundraisers said her donors remain enthusiastic.
"A big boon to the fundraising has been these appeals for her to withdraw," said Larry Stone, a Clinton fundraiser in Silicon Valley who also is the Santa Clara County assessor. "It makes supporters angry, especially women."
Clinton's event Wednesday, in Menlo Park, was chaired by venture capitalist John Doerr. One of Obama's hosts is oil heir Gordon Getty.
Next week, singer Elton John will help Clinton raise cash with a concert at Radio City Music Hall in New York that is expected to bring in more than $1.5 million.
The fundraising represents a respite from campaigning, predominantly in Pennsylvania and almost singularly devoted to the economy.
Sensing a target in McCain, both Obama and Clinton lately have taken aim at the Arizona senator and presumed Republican nominee. Obama has linked McCain to Bush's policies in Iraq and, in her new ad, Clinton portrays McCain as unwilling to tackle the nation's housing crisis.
The ad is a variation on her highly publicized "3 a.m." ad against Obama in which she cast herself as better able to handle national security crises. That ad ran in Texas.
In this ad, a phone rings as children sleep and grown-ups pore over paperwork in their homes.
"It's 3 a.m., and your children are safe and asleep, but there's a phone ringing in the White House and this time the crisis is economic," an announcer says. "Home foreclosures mounting, markets teetering. John McCain just said the government shouldn't take any real action on the housing crisis, he'd let the phone keep ringing."
McCain opposes aggressive intervention by the government to solve the mortgage crisis and the market upheaval it spawned, saying he prefers only limited intervention and letting market forces play out.
Clinton is trying to make a case to both voters and Democratic Party insiders - the superdelegates who may decide which candidate becomes the nominee - that she is better equipped to take on McCain in the general election than Obama.
In the teleconference with reporters, senior Clinton adviser Mark Penn made a point of highlighting polls that show Clinton better positioned than Obama to beat McCain in key states.
"We think her experience and ability to be a commander in chief and her ability to go up against Senator McCain on the economy are key reasons why both a lot of voters and, in the end, superdelegates will look to Senator Clinton as the right nominee for the party," Penn said.
McCain's campaign dismissed the Clinton criticism.
"With ads like that it's most likely that the call she gets at 3 a.m. is, `Senator, you just lost another superdelegate,"' said McCain spokesman Steve Schmidt.
