WASHINGTON – A prominent Republican political consultant severed his ties with Wal-Mart on Friday night, forced to resign in fallout from a controversial political ad in Tennessee’s Senate campaign.

In submitting his resignation, Terry Nelson said Wal-Mart had “come under political pressure from liberal special interest groups” as well as labor unions. “It’s unfortunate that this pressure has had an impact on Wal-Mart.”

In an interview, he said of the commercial that critics deemed racist:

“There was no intention to offend anybody and it’s unfortunate if people took offense. That was certainly not what people planned for or hoped for.”

The ad had no direct connection with Wal-Mart, but the reaction by civil rights activist Jesse Jackson and other critics – and the company’s reaction – underscored the extent to which even the world’s largest retailer can feel compelled to respond to political pressure.

Nelson is in charge of an independent political unit, financed by the Republican National Committee, that recently aired the commercial in a tight Senate race between Democratic Rep. Harold Ford (news, bio, voting record) Jr. and Republican Bob Corker, the former mayor of Chattanooga.

It showed a white woman saying she had met Ford, who is black, at a Playboy Club party. The commercial ended with the woman, her bare shoulders visible, looking into the camera and whispering, “Harold, call me.”

The commercial does not mention that Ford is black, but Jackson and union-funded WakeUpWalmart.com had jointly called on Wal-Mart to fire Nelson to show it does not tolerate racism.

Initially, company spokesman Dave Tovar had said “it would be absurd for us to comment” on the controversy.

But Nelson’s resignation letter to Wal-Mart executive Leslie Dach said he was ending his ties with the company at its request.

Tovar quickly issued a statement saying, “We believe this is the right course of action.”

Not long afterward, WakeUpWalMart.com claimed credit for Nelson’s departure, saying it had threatened to air radio and television commercials demanding his dismissal.

Nelson’s political work for Republican candidates is separate from his company, Crosslink Strategy Group. The firm has had a contract with Wal-Mart as well as with Working Families for Wal-Mart, a separate, company-funded group. Part of the work involved creation of a voter registration program for Wal-Mart employees.

Wal-Mart has labored in recent years to combat charges that it exploits its employees, who are called associates, by paying them low wages and offering substandard health insurance benefits or none at all.

As part of its effort to improve its reputation, it has hired prominent Republicans and Democrats alike. Nelson was the political director for President Bush’s 2004 re-election campaign. Dach, the company official to whom the resignation letter was addressed, has worked in the past for numerous Democratic presidential candidates.

In a brief telephone interview, Nelson said Ford himself had said the ad wasn’t racist.

“I think that the ad was designed to deal with an issue that Harold Ford had put before the voters of Tennessee, that he was someone they could trust as a moderate or conservative Democrat, both in terms of the policies he put forward and his values,” Nelson said. “We felt Tennessee voters should know both sides of the story.”

Ford has called the ad “smutty,” but has repeatedly declined to say whether he considers it racist.

“They want to scare people about me,” he said of the Republicans behind the commercial. “You have to ask them about race. I don’t focus on those things.”