We know that operatives in modern-day presidential campaigns are supposed to say things that everyone knows are ridiculous — and to do it with a straight face.

Still, there was something surreal, and offensive, about today’s soundbite from the campaign of Senator John McCain.

The presumptive Republican nominee has embarked on a bare-knuckled barrage of negative advertising aimed at belittling Mr. Obama. The most recent ad compares the presumptive Democratic nominee for president to Britney Spears and Paris Hilton — suggesting to voters that he’s nothing more than a bubble-headed, publicity-seeking celebrity.

The ad gave us an uneasy feeling that the McCain campaign was starting up the same sort of racially tinged attack on Mr. Obama that Republican operatives, some of whom work for Mr. McCain now, ran against Harold Ford, a black candidate for Senate in Tennessee in 2006. That assault, too, began with videos juxtaposing Mr. Ford with young, white women.

Mr. Obama called Mr. McCain on the ploy, saying, quite rightly, that the Republicans are trying to scare voters by pointing out that he “doesn’t look like all those other Presidents on those dollar bills.’’

But Rick Davis, Mr. McCain’s campaign manager, had a snappy answer. “Barack Obama has played the race card, and he played it from the bottom of the deck,” he said. “It’s divisive, negative, shameful and wrong.’’

The retort was, we must say, not only contemptible, but shrewd. It puts the sin for the racial attack not on those who made it, but on the victim of the attack.

It also — and we wish this were coincidence, but we doubt it — conjurs up another loaded racial image.

The phrase dealing the race card “from the bottom of the deck” entered the national lexicon during the O.J. Simpson saga. Robert Shapiro, one of Mr. Simpson’s lawyers, famously declared of himself, Johnny Cochran and the rest of the Simpson defense team, “Not only did we play the race card, we dealt it from the bottom of the deck.”

It’s ugly stuff. How about we leave Britney, Paris, and O.J. out of this — and have a presidential campaign?