(CNN) Mississippi Sen. Cindy Hyde-Smith and her Democratic rival Mike Espy spent a whopping $6.6 million in the final weeks of a hard-fought Senate campaign marked by a controversy over her comments that evoked a painful chapter in state history.

Hyde-Smith spent more than $1.7 million on the way to beating Espy in last month's runoff and saving her seat -- more than she had spent during any other period in the campaign, a new filing with federal election regulators shows. Espy's expenditures topped $4.8 million, as the former Agriculture secretary drew national attention and donations in his attempt to become the state's first black senator since Reconstruction.

Hyde-Smith's comments about attending a "public hanging" sparked weeks of controversy, given the state's history of racially charged lynchings. And it prompted major corporate interests, ranging from health insurance giant Aetna to Facebook to Major League Baseball, to demand refunds of their political donations.

Her campaign's filing Thursday with the Federal Election Commission shows she returned contributions to three individuals -- including San Francisco Giants' principal owner Charles Johnson and his wife, Ann, who each donated the $2,700 maximum.

In addition, three political action committees also saw their money returned -- MLB, Amgen and the National Cattlemen's Association, although the filings indicate that MLB and Amgen received refunds by stopping payments on their checks. The three PACS had contributed $5,000 each.

In all, the campaign lost a little more $23,000 through refunds and stopped payments in November and December.

Smith's campaign did not immediately respond to requests for more information Thursday.

Other companies say they still are waiting for refunds.

On Thursday, T.J. Crawford, a spokesman for Aetna, told CNN via email that company officials have "made the request, but the funds have yet to be returned."

Aetna's political action committee had donated $2,500 and pledged on Twitter last month to donate the money to anti-racism efforts.

Medical device maker Boston Scientific, which also has sought a refund of its $2,500 PAC contribution, still hasn't received one, spokesman Kate Haranis said Thursday.

"But we've followed up several times with the Senator's fundraising team and they have confirmed receipt of our request," she said in an email to CNN.

Earlier this month, a slew of other companies told the New York Times they were still seeking refunds.

Thursday's filing by Hyde-Smith's campaign covered activity between Nov. 8 and Dec. 17.

And the post-election accounting indicates that handing over all the refunds that have been requested might drain Hyde-Smith's resources: The campaign had just $63,744 remaining in its bank account as the filing period ended, and she's up for re-election in less than two years.

Federal campaign-finance rules require candidates to return illegal or excess contributions, but they do not do not mandate that candidates refund money on demand from disenchanted contributors.

Hyde-Smith beat Espy in the November 27 runoff. She had been appointed in April to fill the seat of Thad Cochran, who retired for health reasons. She is expected to be on the ballot again in 2020 to seek a full, six-year term.

Hyde-Smith's joke about attending a public hanging if invited by a supporter became public November 11 and quickly went viral. She later apologized during a debate with Espy, but said her words had been twisted for political gain.