They were echoing the party line of an inherited economic "mess" even before the president delivered it. And by the time the 1982 Republican Senate-House Campaign dinner was over last night, they were nearly $3 million richer.

"There are people who are sharpening their pencils tonight who will talk about this dinner, write about this dinner," President Reagan told nearly 3,000 at the $1,000-a-plate fund-raiser at the Washington Hilton. "It will be listed as the ultimate in wealth. We, of course, will be referred to, as we are so often, as the party of the rich."

It isn't true, the president continued, nor is it what the Republican party wants to be.

"I guess no party wants to be that," he said. "But I'll tell you what I think we can be proud of. We're the party that wants to see an America in which people can still get rich."

This campaign year, the Republican Party has been seeing to it that it, at least, is getting rich. So far, it has raised an estimated $5 million from two dinners, or about five times more than the Democrats raised in their congressional campaign dinner a little more than a month ago.

Before last night's affair, high-ranking GOP sources said they expected to equal the $3.5 million raised a year ago. But there was some speculation that the president's dispute with Oregon's Sen. Bob Packwood, the chairman of the GOP Senate campaign committee who had been critical of Reagan on the budget deficit and other issues, may have cost the party $500,000.

Politics being politics, bygones were bygones last night and Reagan settled in congenially at a head table that included Packwood; his cochair in the House, Rep. Guy Vander Jagt of Michigan, and Joe M. Rodgers, dinner chairman.

The division of duties worked out this way: Packwood got to welcome everybody; introduce the House chaplain; introduce Pearl Bailey, who led the National Anthem, and ask everyone to be seated and enjoy their dinners. Vander Jagt got to give the other main speech of the evening.

Like the president, who spoke after him, Vander Jagt's refrain was that "Jimmy Carter left us a sick patient indeed . . . he was the inevitable culmination of 24 consecutive years the Democrats controlled the Congress with their tax and tax and spend and spend."

Earlier, when everybody was filing into the cavernous ballroom where hundreds of blue and white balloons dangled from the ceiling, there wasn't much doubt what the battle cry was going to be in 1982.

For example, from Sen. Alan Simpson of Wyoming, talking about his voting record: " . . . all we were doing was reducing Carter's budget."

Sen. Charles Percy of Illinois: "Most people believe the Reagan administration inherited very high inflation, high unemployment and high interest rates. They can't blame the economy on the Reagan administration. We've only had the first Reagan budget since Oct. 1 and that called for a 5 percent tax cut."

President Reagan brought some examples of his own.

Moving to eliminate waste and fraud, he said, a task force of inspectors general has already found "thousands and thousands of people who've been dead for as long as seven years and are still receiving their benefit checks.

"Now I've heard of cradle-to-grave security," said the president, "but cradle to the pearly gates is something else. Who said you can't take it with you?"

Speaking of "seers and prophets in the financial and political world," he called "some optimistic, some pessimistic who, if they don't know how to predict accurately, know how to predict often.

"It reminds me of a sweet revenge that one businessman had recently when he told the company economist who was jumping out of an upper-story window, 'Don't worry, Herb, you'll be bottoming out soon. "

And of legislators in general, the president said: "I can't tell you the sympathy that I felt for some midwestern legislators whose remarks were tacked upon a bulletin board in the Capitol press room. One said: 'Before I give you the benefit of my remarks I'd like to know what we're talking about.' "