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 . Comment:
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 .