RALEIGH — The North Carolina governor’s race continued to be fought in the courtroom Friday as Democrats disclosed they had filed a lawsuit against GOP gubernatorial candidate Pat McCrory.

Dueling legal briefs were added to competing TV attack ads as the two sides fought over an ad that raised questions about McCrory’s relationship with Tree.com, a Charlotte-based lending and real estate firm.

An attorney for the Democratic Governors Association and N.C. Citizens for Progress sued in Wake County Superior Court, asking a judge to decide the veracity of an ad that the Democrats are running.

The Democrats’ suit was brought Thursday just hours before the McCrory campaign filed papers announcing its intention to sue the Democrats over the ad.

“We proactively filed this complaint because we are confident the facts and the law are on the our side and we refuse to let McCrory’s threats intimidate us or media outlets,” said Michael Weisel, the Raleigh attorney representing the Democrats. “To prove McCrory’s claims are false, we will move forward with discovery and plan to depose McCrory and his associates before November 2012, to answer questions about his business relationships and his contact with public officials.”

The Democrats on Friday began running a slightly different version of the ad, but it still contains the basic assertion – that as mayor McCrory lobbied to get millions of dollars in tax breaks to persuade Tree.com to keep its headquarters in Charlotte. He later was paid $140,000 in 2009, his last year as mayor, when he was put on the company’s Board of Directors.

The purpose of the ad is to undercut McCrory’s argument that he is a reformer who can clean up Democratic scandals in Raleigh.

But Republicans argued the change in the ad was an acknowledgement that it was flawed.

“Gov. Perdue’s political attack machine was hoping that nobody would notice as they quietly switched their TV ad today,” said Rob Lockwood, a spokesman for the state GOP. “It’s clear that they wanted this change to go unnoticed as they released this new spot without any promotion or fanfare. The Perdue attack machine’s hushed-up switch should serve as proof that their old ad was as charged: dishonest and misleading.”

The Republican Governors Association, meanwhile, began running an ad attacking Democratic candidate Walter Dalton for high taxes.

“Dalton has consistently voted to increase taxes,” the ad states.

It says North Carolina has the highest business taxes in the South. And it claims that raising the sales tax by three-quarters of a cent would cost 8,000 jobs.

The Dalton campaign said Dalton had voted to eliminate the sales tax on food in 1997, eliminate the marriage penalty in 2001, create a tax deduction for the state’s college savings plan in 2006, and cap the gas tax in 2006 and 2007. It also pointed out that in 2010 Forbes magazine voted North Carolina as having the third best business climate in the country.

“Pat McCrory’s hypocrisy is dizzying,” said Ford Porter, Dalton’s campaign spokesman. “I know that lobbyists are supposed to be able to talk out of both sides of their mouths, but for McCrory to stand before the media and call for a clean campaign on the same day that his political hatchet men launch another misleading attack is a new low.”

Christensen: 919-829-4532