COLUMBIA, S.C. - The Prosperity physician taking on the Republican Gov. Mark Sanford in June's GOP primary says Sanford is to blame for the loss of the state's top credit rating with Standard and Poor's.

Dr. Oscar Lovelace said Sanford has a knack for not listening to people and his "constant bickering with the Legislature helped to create an unstable business environment."

In the 2002 election, Lovelace was a Sanford campaign supporter and contributor. After the election, Sanford appointed Lovelace as co-chairman of a panel studying the state's health care needs.

A lot has changed since then, Lovelace said as he kicked off his campaign in Columbia on the eve of his 46th birthday.

"I have come to realize that the incumbent governor, Mark Sanford, and I have some honest differences of opinion on important issues," Lovelace said.

"The current administration's failure to attract new industry to South Carolina has caused our state to lag behind others in economic recovery, causing record unemployment and recently led to the loss of our triple-A credit rating," Lovelace said. "Sanford's contentious relationship with the Legislature and inappropriate comments and actions - even an adversarial relationship with the leadership of his own party - have hurt our state's development efforts."

In July, credit rating company Standard and Poor's said the state is not generating enough jobs and its unemployment rate remains too high. The firm lowered the state's rating to AA-plus. The two other major credit rating firms maintained the top-tier ratings on the state's debt.

Lovelace also doesn't like Sanford's push for tax breaks for parents who send their children to private schools or the governor's criticism of public schools. "Gov. Sanford, it seems, has abandoned our public schools," Lovelace said.

Sanford's campaign would not respond to the criticism, but issued a statement saying "candidates seem to get into and get out of races every month or so. Gov. Sanford always keeps his focus on defending South Carolina taxpayers and creating jobs. That's where his focus will remain, regardless of the political calendar."

Lovelace says schools, economic development, health care and abolishing residential property taxes are his top issues.

He says he'll generate a billion dollars to cut property taxes by raising the state's cigarette tax to the national average - almost 92 cents a pack. South Carolina's cigarette tax is the nation's lowest at 7 cents a pack.

Lovelace said Sanford's priority has been an income tax break for the wealthy, not working people and older residents.

Lovelace is the only Republican so far to challenge Sanford in the primary. Bob Royall, a former state commerce secretary and former U.S. ambassador, considered running against Sanford, but last week said that his age - 70 - leaves him without the energy needed for a campaign.

Two Democrats, Clearwater Sen. Tommy Moore and Florence Mayor Frank Willis are seeking their party's nomination.

Lovelace remains "a distinct underdog and it's unlikely he could win the Republican primary," College of Charleston political science professor Bill Moore said, adding that Sanford has significant financial resources and is popular with voters.

Lovelace's "greatest impact would be to perhaps embarrass the governor or a wake-up call if he gets 25 (percent) to 30 percent of the vote in the primary," the professor said.

In July, Sanford's campaign reported it had $3.4 million on hand. Lovelace said Thursday that he has raised about $100,000.

"This is a campaign not about money, but about people," Lovelace said.