A $2.8 million debt remaining from Sen. John Glenn's unsuccessful presidential campaign in 1984 is beginning to haunt the Ohio Democrat's reelection bid.

Rep. Thomas N. Kindness, Glenn's Republican challenger, is broadcasting radio commercials here and in three other Ohio cities charging that Glenn has asked four banks for "special treatment" to avoid paying interest or principal this year on $1.9 million owned them.

"John Glenn has said himself that he is morally responsible for these debts, but now John Glenn is asking these four Ohio banks to let him off the hook for a year without any payment so his bad debts won't affect his Senate campaign," the Kindness ads say in a tone of disbelief. "That's wrong. That's not fair. It's probably illegal."

The loans date to February 1984 when three banks in Columbus and one in Cleveland gave Glenn a $2.5 million line of credit to keep his fledgling presidential campaign afloat. The only security on the loans were 18 "letters of comfort" signed by Glenn supporters.

The loans were to have been repaid in full by January 1986, but Glenn has repaid only $110,000 on the principal and $356,073 in interest. Last December, he asked the banks to extend the repayment deadline to March 1987 and permit him to skip monthly interest payments until that time. No interest payments have been made since last November.

The banks extended the deadline until May 15, but have made no decision on what to do beyond that. If another extention is granted, Kindness has threatened to file a complaint with the Federal Election Commission.

"What we're trying to do is put a little pressure on the banks," said Mark Mills, a Kindness campaign spokesman. "We're confident that another extension beyond May 15 is illegal and would amount to a contribution to Glenn's Senate campaign."

Glenn is not the only 1984 Democratic presidential candidate with lingering debts. Sen. Gary Hart (D-Colo.) owed about $3.3 million at the end of March, and Sen. Alan Cranston (D-Calif.) about $300,000, according to FEC reports.

But Hart decided not to seek reelection, and Cranston has proven far more effective at fund-raising than Glenn, who said he has found it impossible to raise money to repay the debt and finance his reelection campaign at the same time.

"It's very hard to raise money for debt retirement. People would rather give for something in the future than in the past," he said in an interview. "People say that race is over and the money is going down the rat hole. They don't like to pay for other peoples' mistakes.

"There isn't much you can do except throw yourself on their mercy and say I need help," the second-term senator added.

"I'm not trying to duck out of this," Glenn said. "I look at it as a debt that will be paid."

Glenn's Senate campaign began the year with $246,000, the smallest war chest of any of the 27 incumbents seeking reelection. Glenn holds a wide lead in public opinion polls, but the Republican National Senatorial Committee thinks enough of Kindness' chances that it plans to pump $700,000 into his campaign after Ohio's primary next Tuesday.

In addition to his bank debt, Glenn owes more than $1 million to hotels, car rental agencies, airplane charter companies, printing firms and former campaign workers. An unpaid bill at the Capitol Plaza Holiday Inn in Des Moines, where Glenn and campaign workers stayed during the Iowa caucuses, totals $24,972.

Glenn, a multimillionaire, said he is personally prohibited from paying the campaign debt himself because of a $50,000 limit on the amount a candidate who receives federal matching funds may donate to his own campaign.

He has already contributed that amount.

No one has ever tested that law, according to a spokesman at the Federal Election Commission.