Presidential contender Pat Robertson may have the last word at the Republican nominating convention this year, even if he isn't the candidate of choice.

Robertson has such a bad taste in his mouth about opponent George Bush that he has told his aides he will throw all his delegates behind the man most likely to defeat him. That man is likely to be Sen. Robert J. Dole (R-Kan.), and the addition of Robertson's delegates in a neck-and-neck race could push Dole over the top.

A former television evangelist, Robertson is an affable man who believes in dealing with people on the up-and-up. He likes to play fair. No questionable deals. No dirty tricks.

Our sources in the Robertson camp say the candidate doesn't think Bush has played fair in return. It began with a less-than-warm telephone call between the two men last year and culminated with what Robertson claims were "dirty tricks" played on his campaign. He suspects the pranksters were in Bush's camp.

Last September, before he announced his candidacy, Robertson made a courtesy call to Bush to inform him that he was running. A source close to Robertson told us that he saw it as a "Christian gesture" to give the vice president advance notice. They talked about keeping the race clean, and Robertson said he wanted to remain friends, come what may.

We asked Robertson recently about the call. Ever the gentleman, he told us that the conversation was cordial. But he gave a different impression to one of his aides right after the phone call; he told the aide Bush had been less than receptive.

Not long afterward, Robertson became convinced that Bush campaign manager Lee Atwater was playing sophomoric tricks. Atwater has a reputation among Republicans and Democrats as a prankster.

According to Robertson, the pranks began when someone canceled hotel reservations for his staff, vandalized automobiles and spread false scheduling information about Robertson news conferences. In New Hampshire, someone wielding a hacksaw vandalized a telephone system that Robertson volunteers had planned to use to encourage voters to go to the polls.

"There's something dirty going on," Robertson told us.

Ed Rogers, a spokesman for Atwater, said Robertson's charges were "ridiculous." Atwater "doesn't spend his time that way," he said.

Robertson didn't blame the pranks on the Dole campaign, because Dole staffers have been victims of similar tricks.

No matter who the prankster is, Bush is likely to pay for it. The decision by Robertson to pledge his delegates to Dole could swing the nomination. Robertson picked up delegates in Iowa and New Hampshire and is likely to pick up more on Super Tueday, March 8, in southern states. He has enthusiastic supporters who will show up at the polls rain or shine and is likely to do well, especially if voter turnout is light.

A bloc of Robertson delegates delivered at the convention could be just the ticket for Dole, not to mention a sweet tit-for-tat for Robertson.