INDIANAPOLIS (AP) _ Democrat Evan Bayh, the nation's youngest governor, has such a commanding lead in his re-election bid that even Indiana's Republican bent in presidential voting is unlikely to reverse it.

Polls show the 36-year-old Bayh, son of former Sen. Birch E. Bayh, has a better than 2-to-1 lead over Republican Linley E. Pearson, the state's three- term attorney general.

''I don't consider this race a lock, but the polls are very encouraging,'' said Ann M. DeLaney, executive director of the state Democratic Party and Bayh's campaign manager.

Indiana, the home state of Vice President Dan Quayle, has favored Democratic presidential candidates only four times in this century, the last time in 1964 with Lyndon Johnson.

Polls show Quayle's boss, President Bush, in a statistical dead heat with Bill Clinton. But Bayh, who broke 20 years of Republican rule in the governor's office with his victory in 1988, has a cushion approaching historic levels.

An Indianapolis Star poll published Oct. 11 showed Bayh with a 67-28 edge over Pearson. The margin of error was 3.5 points in the telephone poll of 803 registered voters.

The advantage is even greater than the newspaper's poll of early September and the 48.4 percent to 16.6 percent spread in a Indiana University-Purdue University at Indianapolis poll at the end of September.

''There is only one election I can recall that was this lopsided at this point in the campaign, and that was when Sen. Richard Lugar set a record for plurality (68 percent) in 1988,'' said pollster Brian S. Vargus.

Bayh is seeking to become only the third Democrat to serve two full four- year terms, joining Joseph Wright, 1849-57, and Henry F. Schricker, 1941-45 and 1949-53. For more than a century, a sitting governor could not succeed himself.

Republicans say the race could change now that Pearson has begun his television advertising campaign. The GOP nominee won a bruising and expensive three-way primary in May and had to spend most of the summer and early fall raising money to try to compete with Bayh.

''Linley's name identification is way down, but I'm sure once he goes on TV, he's going to get more of our base vote,'' said state Republican Chairman Rex Early.

Bayh has virtually ignored his challenger. He runs television ads celebrating his success in helping lure United Airlines' huge maintenance center to Indianapolis and in avoiding a general state tax increase during the recession.

Pearson, 46, has made a no-new-taxes pledge, and he criticizes Bayh for letting local property taxes rise and for rescinding a one-year decrease in auto excise taxes.

The Republican also points out that Bayh has signed three consecutive deficit budgets, using lottery profits, accounting techniques and some of the state's reserves to spend more than what was taken in.

Bayh has declined to take the no-new-tax pledge.

Pearson also has tried to draw Bayh out into more public debate, but the incumbent has declined after making one joint appearance. At that appearance on a cable television show, Pearson used the words ''con game'' and ''fraud'' to describe Bayh's fiscal stewardship.

''If he wants to conduct that kind of campaign, that's OK, but I certainly don't intend to participate in that and I don't intend to give him a forum for that kind of negative mudslinging,'' said Bayh.

Pearson responded: ''Bayh is scared because he does not have answers to the questions about his fiscal record and he's afraid to talk about the future.''