Hey, don’t worry about this.  I’m sure his stance has evolved in the last seventeen years:

Actually, I’m here to defend Mitt Romney, not criticize him, over this ad — and to defend negative campaigning in general.  In 1994, the dynamics of running against a Kennedy in Massachusetts made it strategically advantageous to run as a big underdog in the race.  Romney played it smart by running this ad, which strongly implied that Kennedy was using his money to bully Romney unfairly because Kennedy had run out of ideas having spent his life in Washington.  It didn’t unseat Kennedy, but Romney’s bid was a long shot among long shots in the first place.

Furthermore, political campaigns should focus on the records of the candidates involved, and that’s going to involve criticizing opponents — even in primaries.  That may be “cynical, old-style politics,” but it’s “old-style” because it works.  Every successful campaign I’ve ever seen has employed both positive and “negative” ads in a balance that keeps the overall tone of the campaign more positive than negative.  Even Newt Gingrich has had no problem reaching into the past records of his “competitors,” as Gingrich likes to call his fellow Republicans, and he’s certainly — and appropriately — gone “negative” on Barack Obama.  (Of course, Gingrich says that he’s limiting his no-negative campaign pledge to the primary, in order to avoid damaging the eventual nominee.)  Gingrich has criticized Romney in debates on health care, and attacked Romney on his Bain experience from the campaign trail, although he later semi-apologized for it.

Besides, there is nothing inherently wrong with “negative” ads, as long as they stick to the facts.  How else will a candidate have their records and positions vetted?  The candidates are certainly not going to get up on the stump and say, “Well, I’ve outlined all the ways I’m totally wonderful, so now let me tell you about my mistakes and errors.”  Negative ads can and often do tell half-truths, take statements out of context, and sometimes tell outright lies, but voters need to do their homework, too — and the candidates can answer those with the truth and expose their opponents as misleading and/or dishonest.  And positive ads often tell half-truths, take points out of context, and sometimes tell outright lies, too.

The only criticism that can be made of this ad in the current campaign context is that these recurring public challenges to stop attacking end up making politicians look a little hypocritical at some point in the future.  Even that process reversal has become so ubiquitous in elections that’s barely worth mentioning.