WASHINGTON (AP) _ Two presidential candidates decided at the last minute that they couldn't cede the Madonna set to baby boomer Bill Clinton and turned up Sunday night on MTV.

Independent Ross Perot played the Dutch uncle, dispensing lectures and stern advice about sex, drugs and voting. President Bush ended up on the defensive on subjects ranging from taxes and abortion to the motor-voter bill. Both interviews were taped.

Clinton appeared on the music-video cable station in June, answering audience questions and promising that if elected, he would return to MTV as president. MTV's coverage of the campaign has been aimed at young voters.

Initially Bush dismissed the idea of going on MTV. ''I think in a campaign year you've got to draw the line somewhere,'' he said in June. ''And I am not going to be out there kind of being a teeny-bopper at 68. I just can't do it.''

But times and strategies changed. So on Saturday, he submitted to an interview as his train rolled through Wisconsin.

He was asked if it was fair that a couple making $53,000 in 1991 paid a 28 percent tax rate while the president and his wife, with a $1 million income, paid 16 percent.

''Did you say how much we gave away there?'' Bush asked, and said he had contributed the whole $1 million to charity. As for the tax rate differential, he said, ''I think it's fair'' and added, ''I'm for lower taxes as far across the board as possible.''

Perot got easier questions from a different interviewer and directed most of his remarks straight to his audience.

''Stop irresponsible sex,' he said emphatically. ''Just remember everytime you start thinking about it that Ross said you're not a rabbit.''

He told young men: ''You're dirt if you create a baby and you don't take all the responsibilities of a father... That's not a man, that's not a boy, that's a jerk.''

He told drug abusers: ''You're a burden to society, and you're selfish.''

The Bush interview steered clear of some touchy issues - the administration's Iraq policy and Bush's role in the Iran-Contra affair.

An MTV spokeswoman, Carole Robinson, said those were the conditions put on the interview by the Bush campaign. The White House denied conditions had been set, but Robinson said that was ''absolutely not true.''

On other subjects, Bush said he vetoed the bill that would have allowed registration when a person got a license because he was concerned about possible fraud. He also said he believes in the abortion-counseling ''gag rule'' on health professionals at federal funded birth control clinics because only doctors should discuss abortion with clients.