(Bloomberg) -- Elizabeth Warren’s campaign defended the transfer of more than $10 million from her Senate campaign account to her presidential bid after Joe Biden suggested the move violates the fundraising restrictions she’s put in place for the 2020 race.

“We’re pleased that our grassroots strategy has been so effective that they’re now threatened enough to be attacking us for it,” Warren spokesman Chris Hayden said in a statement Friday. “They’re right to be worried because we intend to win and bring structural change to end the stranglehold of big money on our political process.”

Biden told reporters this week that his campaign is at a cash disadvantage in part because “we did not start off by dropping $10 million from a Senate campaign -- wherever that money was raised -- into a race.”

His comment was a not-so-veiled shot at Warren, who on Tuesday said her campaign would no longer accept “any contributions over $200 from executives at big tech companies, big banks, private equity firms, or hedge funds” and would refund contributions that have already been made. The decision comes on a top of a previous announcement of a ban on high-dollar fundraisers for her campaign.

But Warren had no such restrictions in place for her Senate re-election in 2018, when she raised $25.8 million, of which a campaign aide said $6 million was netted at “big dollar” events.

To the Biden team, Warren’s use of the Senate money in the presidential race adds ammunition to its argument that she is not being “straightforward” with voters, a theme Biden hinted at during Tuesday’s Democratic debate in Ohio.

Now, the Biden camp wants Warren to explain why the transfer of $10.4 million during the first quarter of 2019 does not violate her fundraising pledge.

“Senator Warren has yet to explain whether she plans to raise taxes on the middle class to pay for her $30+ trillion health care plan, or why the $10 million transferred from her Senate campaign to her presidential fund doesn’t violate her pledge,” Biden spokesman TJ Ducklo said. “We’re not going to beat Donald Trump with double talk and dodgy answers.”Biden’s pressure on Warren’s fundraising practices comes as he’s fallen behind in raising money. After keeping pace with other top Democratic candidates during his first three months in the race, Biden’s campaign is now in tougher financial shape than those of many of his rivals.

Biden raised $15.7 million and spent $2 million more than that during the third quarter and ended the quarter with $8.98 million in the bank. That’s millions less than the Bernie Sanders, Warren, Pete Buttigieg and Kamala Harris campaigns, according to campaign finance disclosures filed on Tuesday. Warren had $25.7 million cash on hand, second only to Sanders, who had $33.7 million.

Biden’s campaign has argued that it’s been racing to build infrastructure after a later start than others and without the advantage of a stockpile from another campaign account, as he last ran for office on his own in 2008.

Transferring money between federal campaign accounts is a common practice for presidential hopefuls and has also been done by Sanders and Harris, among others in the 2020 race. And, when Biden ran for president in 2008, he transferred close to $3.7 million into his presidential account.

To contact the reporter on this story: Jennifer Epstein in Washington at jepstein32@bloomberg.net

To contact the editors responsible for this story: Wendy Benjaminson at wbenjaminson@bloomberg.net, Max Berley, John Harney

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