Hillary Clinton's campaign boosted spending 28 percent last quarter from the one before, blowing through $33.1 million. | Getty Sanders challenge drains Clinton machine

The Clinton fundraising juggernaut is beginning to show signs of strain in the face of an escalating challenge from Bernie Sanders.

Hillary Clinton's campaign boosted spending 28 percent last quarter from the one before, blowing through $33.1 million, to Sanders' $32.3 million. Both Democrats outspent any of the Republicans, with Ben Carson the closest behind, having spent $27.3 million. The campaign owed almost a million dollars more to several of its main vendors.


Clinton reported just under $38 million cash on hand at year-end after bringing in $38 million, according to her filing with the Federal Election Commission late Sunday night. But unlike Sanders, with his hordes of small donors, only 15 percent of Clinton's money came in checks smaller than $200 last quarter, and more than a third — $14.6 million — came from donors who aren't allowed to give any more.

Lawyers and bankers figured prominently among her donors. The top 10 employers of her contributors were the law firms Paul Weiss, Kirkland & Ellis, Jenner & Block and Sidley Austin; Cantor Fitzgerald, Lazard and Morgan Stanley; Stanford; Google; and healthcare company Centene, according to the FEC report.

The candidate herself sunk another $89,000 into the effort, bringing her total to $368,000.

A quarter of the campaign's outlay ($8.7 million) went to GMMB, the firm of her media advisor, Jim Margolis.

The 700-strong payroll swallowed up $7 million, and $957,000 went for rent at 50 separate companies.