CHARLESTON, W.Va. (AP) _ Former Gov. Arch A. Moore, a Republican who served three terms in a heavily Democratic state, could serve up to 36 years in prison for kickbacks, coverups and other crimes committed in his last term and two campaigns.

His Democratic successor, Gov. Gaston Caperton, said Moore's decision Thursday to plead guilty to five federal charges helps explain the state's current severe financial woes.

''I am confident that West Virginians will realize that not only did I inherit a government that was financially bankrupt, but ethically bankrupt as well,'' Caperton said.

''This is a tragic day for West Virginia,'' Caperton added.

A grand jury indicted Moore on Thursday and he signed a plea agreement later in the day, U.S. Attorney Michael Carey said. He said Moore had agreed to help prosecutors in other, unspecified corruption probes.

Moore, the charismatic, silver-haired patriarch of the state GOP, admitted to extortion, mail and tax fraud to get elected in 1984, during his term as governor and in his unsuccessful 1988 re-election campaign, Carey said.

Moore also admitted blocking a federal grand jury investigation of him during 1989 and 1990.

''This news will be greeted with a great joy by some in the state of West Virginia,'' Moore said in a statement. ''There will be others who will be sincerely grieved by reason of their devotion to me and my family. I know I have their understanding and love.''

Moore, who turns 67 on Monday, faces up to 36 years in prison and $1.25 million in fines. Carey said Moore should appear in court within two weeks.

Many West Virginia politicians have either become involved in corruption scandals or resigned recently. Since December 1988, a state attorney general, a state treasurer, two state Senate presidents, a Senate majority leader, a top aide to a Senate president, a House member and two lobbyists have lost their jobs.

It is the second time Moore has been indicted by a federal grand jury for alleged wrongdoing in office.

Moore was governor from 1969 to 1977 but was constitutionally barred from seeking a third consecutive term. He and his 1972 campaign manager were indicted in December 1975 on a charge of extorting $25,000 from a businessman seeking a state charter for a new bank. Both were acquitted in 1976.

The indictment said Moore used his position to extort $573,721 in October 1985 from Maben Energy Corp. of Beckley, a coal mining and processing company, and H. Paul Kizer, the company's chairman.

Moore allegedly agreed to help Kizer and Maben Energy receive a refund of more than $2 million from the state's black lung fund, which provides benefits to coal miners with the respiratory disease. In return, Moore received a 25 percent kickback, the indictment said.

It said Moore created fake, backdated documents purporting to be legitimate ''contingent fee'' legal agreements to cover up the extortion.

The indictment also said Moore filed false federal income tax returns for 1984 and 1985, failing to report $72,500 in income, and that he defrauded the state of his salary and benefits by funneling about $100,000 into his 1984 campaign fund.

It said Moore committed the crimes to influence votes and win the governor's race.

Moore also agreed to plead guilty to one count of obstruction of justice. The indictment said he falsified documents, tried to persuade witnesses to lie to a grand jury and lied in an interview with federal investigators.

In early January 1990, Moore met with former aide and 1988 campaign manager John Leaberry. ''Unknown to Moore, his meeting with Leaberry was recorded,'' Carey said.

Moore allegedly told Leaberry that he had received and used illegal cash in the 1988 campaign and told Leaberry how they would both falsely deny the existence of the cash, the prosecutor said.

Moore first was elected to the House of Delegates in 1952. He won a seat in the U.S. House in 1956, serving six two-year terms before his first gubernatorial bid in 1968.

Democrats hold a 2-to-1 edge in registration in West Virginia.