Donald Trump has to deal with his much-criticized debate performance. His poor poll numbers. A national political director who has all but disappeared less than three weeks before the election.

But behind the scenes there are ominous signs of even deeper problems.

The candidate’s expenditures on legal fees have already caught the eye of campaign watchdogs, who say such unprecedented rates of spending suggest there are as-yet-unknown controversies bubbling beneath the surface of the businessman’s organization.

The campaign financial disclosures for September, released Thursday night, seem only to reinforce those worries: The Trump campaign spent more than half a million dollars on lawyers in just one month.

By way of comparison, Mitt Romney’s campaign spent just $1.15 million over the course of his entire 2012 presidential campaign. Trump’s spending on lawyers now tops $3 million.

“Hard to say if any of these legal representations represents a serious problem for the campaign, since we don’t know the subject matter of each one,” campaign-finance lawyer Brett Kappel told The Daily Beast. “The overall level of spending on legal fees, however, remains extraordinarily high, indicating that there must be a great deal going on behind the scenes we don’t know about.”

Trump’s legal fees would be astronomical for any conventional political candidate, but of course the Republican nominee has a knack for drawing controversy, and all the lawyers that entails.

His charity has come into question after being improperly used for political purposes; and the campaign has experienced unprecedented turnover among senior staff, including the departures of managers Corey Lewandowski and Paul Manafort, former Trump delegate manager Ed Brookover, and communications aide Michael Caputo.

But the legal nightmare may just be beginning. It was not until early October that a recording of Trump bragging about sexual assault was released, prompting a wave of accusers to step forward and allege sexual misconduct by the Republican nominee.

Trump’s spending on lawyers has been distributed over a number of law firms.

The fourth highest expenditure for legal spending, more than $55,000, went to an organization called Parliamentary Strategies LLC, which shares an office address with Harvey & Binnall PLLC. Jesse Binnall, a partner at the firm, is a parliamentarian who previously represented Dimitri Kesari, a former aide to Ron Paul’s 2012 presidential campaign. Kesari was sentenced to three months of house arrest and paid a $10,000 fine for a plot to pay for an endorsement ahead of that cycle’s Iowa caucuses.

Over the course of September, Trump spent about $320,000 on his primary law firm, Jones Day. The campaign spent $34,000 more on New York law firm Larocca Hornik Rosen Greenberg & Blaha. It also paid more than $70,000 to Chicago’s Locke Lord LLP and $3,000 to Michael A. France Trust in Sarasota, Florida.

The Trump campaign also spent more than $21,000 on “research consulting” with O’Melveny and Myers, a prestigious law firm headquartered in California; and thousands more for lawyers at Belkin Burden Wenig & Goldman, as well as Bell, McAndrews & Hiltachk.

With just a few weeks left until Election Day, the Trump campaign’s spending on lawyers portends a long road ahead for the Republican nominee—even as the campaign season winds down, his legal troubles may not.