WASHINGTON ( CNN ) -- Sen. Barack Obama raised more than $ 40 million from more than 442,000 donors in March , his presidential campaign announced Thursday . Sen. Barack Obama greets campaign volunteers during a stop in Philadelphia , Pennsylvania , Wednesday . More than 218,000 of the donors were giving for the first time , the campaign said . The figures are estimates , a campaign spokesman said . `` We 're still calculating . '' Sources in Sen. Hillary Clinton 's campaign said the New York senator raised $ 20 million in March . Impressive as the $ 40 million figure is , it is well below the $ 55 million Obama raised in February . Clinton , Obama 's rival for the Democratic nomination , raised about $ 35 million in February . Political analysts say this kind of fundraising power catches the attention of voters . `` They add to the so-called 'bandwagon effect ' -- the sense that Obama is building , that he 's going to be the nominee , '' said Stu Rothenberg of the Rothenberg Political Report . With its March totals , the Obama campaign has raised approximately $ 234 million , which surpasses the Democratic record of $ 215 million that 2004 nominee Sen. John Kerry raised in that presidential primary season . Obama is $ 25 million shy of President Bush 's presidential primary fundraising record of $ 259 million , set in his uncontested campaign in 2004 . Obama raised $ 194 million through the end of February . Official fundraising tallies for March are due to the Federal Election Commission by April 20 . Clinton raised $ 156 million through the end of February . The Clinton campaign said Thursday morning it would not release March figures until required to file its FEC report , two days before the critical Pennsylvania primary April 22 . But later , campaign sources provided the figures , which show March to be Clinton 's second-highest fund-raising month for the campaign . A Clinton spokesman downplayed the importance of Obama 's fundraising total . `` We knew that he was going to out-raise us . He has out-raised us for the last several months , '' Howard Wolfson said after Obama 's figures were released . `` We will have the resources that we need to compete and be successful in the upcoming primary states . '' Wolfson also said he expected Clinton 's tax returns to be released soon . Clinton pledged March 25 she would release her returns within a week . Sen. John McCain , the expected Republican nominee , raised $ 11 million in February . He has not announced his March total . E-mail to a friend . CNN 's Rebecca Sinderbrand and Rob Yoon contributed to this report .
NEW : Sen. Clinton raised $ 20 million in March , campaign sources say . Clinton camp says her tax returns will be released soon . More than 442,000 donors contribute to Sen. Barack Obama 's , campaign says . Number is below record $ 55 million Obama raised in February .