Virginia Republican Rep. Stanford E. Parris made sure to spend yesterday morning in his Springfield office while his longstanding Democratic rival, Herbert E. Harris II, was in his own Springfield headquarters a few miles away kicking off his 1982 campaign against Parris.

For a decade, the two Fairfax County politicians have made careers out of watching each other closely.

Harris' announcement that he would run for the 8th District congressional seat officially inaugurated the third and probably final contest between the men, each of whom has gleefully knocked the other out of Congress once.

The race will be monitored not only as the latest battle in a personal war that Harris and Parris have fought with mutual fascination and distaste since the 1960s, but as a popularity test of President Reagan's economic policies and of the futures of the 52 freshmen Republican congressmen Reagan helped sweep into office two years ago.

"Anything we can do for that reelection, we will do," said one national Republican strategist. "I think the Harris-Parris race is going to be a true test of all these programs."

The 8th District, stretching from Alexandria through eastern and southern Fairfax into eastern Prince William and Stafford counties, represents the kind of middle class, suburban swing district that gave Reagan his overwhelming victory in 1980. Harris, then a third-term congressman, was defeated by 1,090 votes out of about 200,000 when Parris convinced enough disgruntled federal workers and worried homeowners that Harris was too loyal a supporter of an ineffective Carter administration.

Harris yesterday returned the favor, painting Parris as an unquestioning booster of a Reagan administration that has favored the rich at the expense of the middle class. "The notion that people voted for a government of special privilege is just crazy," Harris said. "They were not happy with the Carter administration, as neither was I, but they didn't vote for a government of special interests."

The 55-year-old international trade lawyer, speaking to about 100 supporters, listed the themes that he and the Democratic Party hope will retire some of the Republican representatives who came to Washington with Reagan. He attacked the size of the federal budget deficit, pledged "to return equity to taxes," sympathized with retirees and small businesses and asked for more sensitivity toward the environment.

"There is no quick fix to the economic problem," Harris said. "The past year is pretty stark evidence that the quick-fix approach is wrong."

From his Springfield congressional office, Parris reacted by once again linking Harris with Carter and denying that he has followed Reagan blindly. He also put some distance between himself and Reagan, saying he would not support the president's fiscal 1983 budget in its entirety. He added, though, that the president had put the country on the right track.

"For years Herb and his liberal buddies have been throwing money away over there like it was going out of style," Parris said. "The question is, do you want to go back to a guy who supported the Carter administration?"

Parris was elected in 1972 but was defeated by Harris in 1974, when a host of Democrats rode to office on the post-Watergate tide. Harris won by slim margins against other Republican challengers in 1976 and 1978 and then lost to Parris in their second contest in 1980.

Since that time, the Democratic General Assembly in Richmond has redrawn the 8th District boundaries by lopping off solidly Republican territory in western Prince William. The Parris campaign estimated that the redistricting cost them a net loss of 2,800 Republican voters, more than the margin of victory in 1980.

The Harris forces hope that the redistricting, combined with a faltering economy, a strong volunteer effort and the history of success for the party out of power during nonpresidential election years, will overcome what is certain to be a decided financial advantage for the Parris campaign.

Parris outspent Harris about 2 to 1 in 1980, raising more than $500,000. This year he hopes to raise at least $600,000, and he has assembled a high-powered team that includes pollster Robert Teeter, media consultant River Bank, Inc., which will also be working for the likely Virginia U.S. Senate Republican nominee, Paul Trible, and direct mail specialist William Royall, who previously worked for former Virginia Gov. John N. Dalton.

By the end of 1981, Parris had raised $114,752, according to records filed with the Federal Election Commission. Much of the money came from developers, builders and lawyers in Northern Virginia and from national political action committees of bankers, milk producers, insurance firms and energy companies.

Harris had raised $41,401 by the end of the year, much of it from government employe organizations and other labor unions. He said yesterday he hopes to attract $400,000 by November. His campaign hired pollster Peter Hart, who worked in Virginia Gov. Charles S. Robb's successful 1980 campaign, but has yet to pick a media consultant.

Harris will also have to spend some funds fighting for the nomination, since a little-known party activist named Richard S. Spaulding announced his candidacy earlier this week. Spaulding said he will run "an educational campaign" stressing his opposition to nuclear weapons and nuclear energy and support for handgun controls. The Democrats have not yet decided whether to hold a primary or a convention in the district.

The money gap could be widened since the Republican party will be far better financed than the Democrats for the off-year election. In 1980, the Republican congressional committee raised $44 million, compared to less than $13 million for the Democrats. A top Republican party strategist said the party intends to spend all it legally can for Parris.

Rep. Tony Coelho (D-California), who heads the Democratic congressional committee, said Harris is "high on the list" for Democratic help, although a final priority list has not been compiled. "We tell our candidates, 'Don't worry about how much your opponent spends,' " Coelho said yesterday. "Who runs the best campaign is still the bottom line."

Both candidates began the campaign by denying that they dislike each other, while gently lobbing the insults that have become a trademark of their campaigns.

"That is overdone, and it will be overdone again," Harris said. "Stan has an extraordinarily pleasing personality--and taking the stands he does, it really takes an extraordinarily pleasing personality to win ."

"I don't think Herb Harris is evil," said Parris, who earlier decided not to run for U.S. Senate because he did not want to leave an open House seat for Harris. "I just think he's wrong."

The two men have been at odds since they served as Fairfax supervisors in the 1960s. "Stan started out as a zoning attorney. I started out as a civic association president," Harris said. "Zoning attorneys and civic association presidents just don't get along on policy issues."