Sen. Hillary Rodham Clinton has lent her presidential campaign $6.4 million over the past month, a campaign aide says.
The money more than doubles Clinton's personal investment in her bid for the Democratic nomination. She gave her campaign $5 million earlier this year.
Clinton has been struggling financially behind the record fundraising of her Democratic rival, Barack Obama.
Obama has routinely outspent her in primary after primary. Clinton's campaign reported raising $10 million online after her victory April 22 in Pennsylvania. But Obama has shown little difficulty tapping his vast network of donors. He spent more than $7 million on advertising head of Tuesday's primaries in North Carolina and Indiana to her nearly $4 million.