News that the senior senator would hit the presidential campaign trail during the final days of the election sparked sharp criticism from his GOP challenger, Jack E. Robinson.

He's turned his back on the voters of Massachusetts, complained Robinson in a telephone interview. He's turning his back on the state and flying around the country. It's what people who feel entitled do.

Robinson pointedly noted Kennedy was breaking the promise he made just last week to spend all of his remaining time campaigning in Massachusetts after the Senate adjourned.

Kennedy aides insisted the Gore trip - which includes rallies with union members in Oshkosh and Eau Claire, Wis.; Flint, Mich.; and Logan, W. Va. - will only be a minor diversion from his Massachusetts campaign.

It's a limited trip, said Kennedy spokesman Will Keyser. Senator Kennedy feels strongly that electing Al Gore is in the best interests of Massachusetts and the country.

Kennedy, 68, who remains popular with rank-and-file Democrats nationwide, came under heavy pressure to hit the national campaign trail for Gore, who desperately needs to boost party turnout, Gore sources said.

Keyser stressed the senator would be back in Massachusetts for weekend events, including a campaign bus tour from Cape Cod up to the North Shore Saturday.

Kennedy last week announced that he would not debate Robinson or Libertarian Carla Howell, despite an invitation from a media consortium. It was the first time in Kennedy's 38-year Senate career that he has not met his challengers in a formal debate.

The senator's decision came even though he is virtually assured of winning another six-year term.

Robinson's threat to raise Kennedy's Chappaquiddick scandal had alarmed the senator's strategists. Robinson, who had personal controversies of his own, has been disavowed by the state GOP and is running a marginal campaign financed by his own money. Robinson is a telecommunications executive with no political background.

Keyser last week said the senator was unable to debate because he was too busy working in the Senate, which was bogged down in a budget battle pitting GOP leaders against President Clinton and Democrats.

The senator is going to spend the remaining days . . . talking to the voters of Massachusetts about his view of the future, Keyser said last Tuesday.

Yesterday the Senate announced it would recess until after the Nov. 7 election. It will finish its business in a lame-duck session beginning Nov. 14.

Kennedy has been active on the campaign trail in recent weeks for Democrats. Two weeks ago he visited Buffalo to stump with New York Senate candidate Hillary Rodham Clinton.