Vice President Bush, telling a Republican fund-raiser audience that he "can't wait" for the 1984 presidential campaign to begin, tonight attacked several Democratic primary candidates--particularly front-runner Walter F. Mondale--as a "Democratic herd" that does not include a single winner.

The $100-a-plate dinner, preceded by a $1,000-a-couple reception, was the fourth fund-raising event for Bush in three days. In Kentucky on Friday and Saturday he used the annual gathering of the rich and famous at the Kentucky Derby--including former presidents Carter and Ford and former secretary of state Henry A. Kissinger--to make clear that the Republican Party and the Reagan administration think they can keep the White House after 1984.

"It was a thrill to see the Derby ," Bush said, "that thundering pack springing from the starting gate, coming charging along, jockeying for position--and I don't know why, but my mind thought of the Democratic candidates running . . . . One big difference, though: in November '84 you won't find any of the Democrats in the winner's circle."

Tonight he took on consumer advocate Ralph Nader, telling the crowd that the administration remains opposed to federal regulations in principle and to Nader's advocacy of government intervention in industry for consumer protection.

In Kentucky, the vice president called the Democrats "political sugar daddies" for favoring more regulation and more government spending as a payoff to voters despite the adverse effects on the economy.

"I can always tell," he said, "when the presidential campaign season rolls around. It's like these overweight jockeys . . . they start trying to lose weight . . . Gary Hart, I saw him in the steam room the other day, and Fritz Hollings is dropping a few pounds . . . but that Fritz Mondale is still having trouble trying to lose Jimmy Carter."

"Let me give you a little advice," Bush told audiences at each of the fund-raisers. "In the presidential derby, put a little something on the California entry--and I don't mean Alan Cranston."

At a Houston fund-raiser last week, President Reagan attacked Mondale as "Vice President Malaise" and a "bleeding heart" liberal. Bush kept up the assault Saturday and today, saying:

"I heard Mondale say the other day, after they asked him what he would do if elected . . . . 'I'll bring down interest rates.' They were 21 1/2 percent when he left office. How . . . will he bring them down now?