Scott Walker is still working to pay off the debt from his short-lived campaign. (Isaac Brekken/APP)

The presidential campaign committee of Wisconsin Gov. Scott Walker spent $1.4 million last quarter paying former staff and vendors and refunding excess contributions, leaving him with $1.2 million in debt from his failed White House bid, new Federal Election Commission filings show.

Meanwhile, the super PAC backing his candidacy, Unintimidated PAC, had so much money left over it was able to give donors back more than $18 million, including $4 million to Wisconsin roofing billionaire Diane Henricks.

The group's inability to keep Walker in the race, despite its substantial resources, is a key example of the limitations of deep-pocketed super PACs in this election.

Walker ended his bid in September after confronting mounting expenses and dwindling resources. His abrupt departure triggered an intense round of finger-pointing, as supporters blamed campaign manager Rick Wiley for mismanaging the finances and letting costs spiral out of control. Wiley rejected that criticism, saying the campaign was investing in needed resources, but was hampered by shrinking donations.

New FEC filings show that Walker's campaign spent at least $1.9 million on payroll for its ballooning staff. Other major expenses: at least $750,000 that went to consultants and $1.2 million spent on direct mail.

The campaign committee started the fourth quarter with nearly $1 million and raised nearly $500,000 to help pay down his debt, for a total of $7.8 million in contributions. But Walker still owes substantial sums to four dozen vendors and former staffers. The biggest outstanding invoice: $316,680 to FLS Connect, a political data firm that does fundraising and voter contact. The campaign also owes $82,290 to law firm Jones Day and nearly $17,000 to ACS Sound & Lighting.

"Governor Walker made substantial progress in addressing financial commitments over the last quarter, and he remains humbled by the outpouring of support from friends across the country who continue to believe in his commonsense reform agenda," Walker campaign spokesman Joe Fadness said in a statement.