Advisers said Monday that Republican Sen. John McCain has raised more than $15 million in March for his presidential campaign.

The total is his best fundraising month since he began the campaign, but he still raised less than the Democrats in the race, Sens. Barack Obama and Hillary Rodham Clinton. Obama raised more than $40 million in March, and Clinton raised more than $20 million.

The campaign officials spoke to The Associated Press on condition of anonymity because the numbers haven't been made public.

Altogether, McCain has raised about $75 million for his presidential campaign. Obama has raised about $234 million, and Clinton has raised more than $175 million.

Clinton said during a campaign swing through California that both Democrats "are raising huge amounts of money, and I am thrilled at how effective Democrats have been in raising money the last 15 or so months.

"I will have money to compete. Obviously Sen. Obama has more than enough money to compete. But this is a good news story because it means we are raising it from people committed to our candidacies."

Obama's money has given him a significant spending edge over Clinton in Pennsylvania, where the April 22 primary is the biggest delegate prize left on the Democratic calendar. He has purchased more than $2.7 million in television ads in the state, according to data compiled by TNS Media Intelligence/Campaign Media Analysis Group, which tracks political ads. Clinton has spent almost $900,000 on ads in the state.