When John Gnorski read a newspaper story about a projected $28 million shortage in the District of Columbia's revenues, he decided to write a stern letter to Mayor Marion Barry.

Even though the 31-year-old Gnorski is not a District resident, his warning to Barry that how he overcomes the deficit "will be a test of your administration" riveted the mayor's attention.

For Gnorski is not your ordinary suburban commuter. He is staff assistant to Sen. Patrick J. Leahy (D-Vt.), chairman of the Senate Appropriations subcommittee on the District of Columbia, and as such he speaks with all of the senator's authority.

Gnorski, his House counterpart Americo S. (Mico) Miconi, staff assistant to Rep. Charles Wilson (D-Tex.), and other staff members in similar positions wield wide power over the day-to-day operations of the city government.

Their opinions and advice, for example, may decide whether the city will get a convention center, or a downtown campus of the University of the District of Columbia, or how the city's $1.4 billion budget can be spent.

The latest example of Gnorski's clout is the letter that he sent, over Leahy's signature, to Barry last week.

Gnorski conceived the idea of the letter, mentioned it to Leahy on the telephone and wrote it, dated Jan. 31. Five days later, Leahy signed the letter without further conferring with Gnorski or changing a word.

Top city officials not only feel insulated by being forced to respond to telephone calls and letters from Hill staffers, rather than elected members of Congress. They also perceive an undercurrent of racism in what they consider a barrage of meddlesome inquiries from white, suburban congressional staffers, and their white nonresident bosses.

According to Gnorski, City Administrator Elijah B. Rogers, frustrated about the limited home rule granted to officials of the nation's capital, once said Gnorski and Miconi were part of the "white masters of Congress."

Rogers said the other day that he does not recall using that phrase. But he said there was an exchange with Gnorski and Miconi, at a Christmas party in the office of D.C. Budget Director Gladys W. Mack, that grew out of a discussion of the relationship between Congress and the city.

One District official would not go so far as to label Hill actions as overt racism, but said, "Their approach does reflect the attitudes and opinions of the predominant culture."

An aide to Barry said it doesn't help that many of the actions from the Hill are initiated by people who are white and live outside the city.

Leahy lives in McLean, and Gnorski and Miconi live in Alexandria. Wilson lives on Capitol Hill. All but one of the 15 congressmen, senators and staffers connected with the two District appropriations subcommittees -- one in the Senate and one in the House -- are white. The exception is Rep. Louis Stokes of Cleveland.

Congressional members and their staffers deny that racism is involved in their actions.

Leahy points to his solid liberal credentials, and adds that he favors full home rule for the city. Until that happens, he said, he will take seriously the job of budgetary control that Congress retains.

Gnorski said he gets "lots of calls" from District residents asking Congress to investigate something, "and most of the complaints come from blacks."

The power exercised by key congressional staffers such as Gnorski and Miconi results from a proliferation of subcommittee assignments that has made it impossible for members of Congress to stay up to date personally on all matters that come before them.

Leahy, for example, must divide his attention among 13 subcommittees, two of which he chairs. The second chairmanship -- of the rural development subcommittee of Agriculture -- is of great importance to Leahy and his Vermont constituents, especially because Leahy is up for reelection this year.

Leahy in effect paid tribute to the authority he has delegated to Gnorski and Gnorski's secretary, Betty Hoem, in an autographed photograph that Gnorski has framed on his office wall. The photo shows Leahy, arms around Gnorski and Hoem, standing before a cake decorated as the D.C. budget. Across the bottom of the photo Leahy has written, "to John and Betty, the real chairpeople of the budget."

The workload in the House isn't much different, although members of the Appropriations Committee are barred from serving on another standing committee. Wilson, however, is quick to say that he leans heavily on Miconi for guidance.

"I've got 700,000 constituents [in Texas] to worry about, plus serving on the foreign operations subcommittee" of Appropriations, Wilson said. "I couldn't get along without Mico. He's so good that I don't have to do much but sit there and preside at the hearings."

Congressional staffers, sitting behind the committee chairmen and whispering facts and opinions in their ears, exert considerable influence over line-item budget decisions, whether the spending request is for defense, agriculture or a federal agency.

But when the subject is the District of Columbia, additional factors come into play. In the first place, District officials resent Congress having so much control over their budget.

"Obviously, they congressional committees) are involved by law in the budget process," City Administrator Rogers said. "But I feel very strongly that we ought to be treated like any other city, and that complete home rule ought to be the goal of this administration."

While some District Building officials complain about "meddling," Congressman Wilson said it was the work of Miconi and Edwin F. Powers, a staff member of the full Appropriations Committee, that "allowed us to ease the budget through the House without restrictive abortion language" last summer.

Gnorski said he had anticipated that the letter he wrote to Barry would prompt "arguments that we're meddling, that it's none of our business. But it is, the law is clear."

He pointed to a provision in the city's budget that says the city cannot transfer, increase or decrease more than $50,000 or 10 percent of a department's funds without congressional approval.

If the mayor were proposing across-the-board cuts to offset the deficit, Gnorski said, "we wouldn't care. But they are being selective" and thus risk subverting the intent of Congress as expressed in the previously approved budget.

"Right or wrong, we are protecting the federal prerogative," Gnorski said.

Miconi says he cannot believe that many people in the District government know his name, much less hold him in either awe or contempt.

"Maybe they refer to me as 'the Hill' or 'the committee', suggested Miconi, who came to the Hill on temporary assignment from the Treasury Department in 1971 and stayed. Miconi, 38, had been recruited for federal service by Treasury just before his graduation from Fairmont State (W.Va.) College in 1963.

For the first seven years as an Appropriations Committee staffer, Miconi was assistant on two subcomittees under Earl Silsby, budget chief to longtime D.C. subcomittee chairman Rep. William H. Natcher (D-Ky.) Miconi advanced to the $40,000-a-year post of chief clerk and only employe of the subcommittee when Silsby retired at the end of 1978.

Because Hill aides are patronage employes, they tend to reflect the views of the elected officials who hired them.

Miconi, an unassuming accountant reflects a benign attitude toward the District government fostered by Natcher, and continued to a lesser degree by Wilson. According to associates, Natcher's philosophy, developed over 25 years on the subcommittee, was that "you could get a lot of adverse publicity by trying to run the District government, especially when you realize that a lot of the money we are voting on is their own, raised by local taxes." Natcher limited his "meddling" to opposing construction of the Metro subway system in favor of highways.

Miconi stayed on when Natcher turned over the chairmanship to Wilson at the beginning of 1979 because, unlike most committees, House Appropriations has a rule that subcommittee chairmen cannot pick their own staffers -- a condition that Wilson said makes that staff "the best on the Hill."

Gnorski grew up in Wisconsin, dreamed of being a forest ranger, and earned a degree in forestry at Wisconsin State University at Stevens Point in 1971. But when he was discharged from the Navy four years later, there were "so many applicants for forest rangers that Interior wasn't even processing new ones," so he took a job in the Bureau of Land Management at Interior.

After eight months he was reassigned to the Capitol as a budget analyst. He switched to the interior subcommittee of Appropriations in 1976. Last March, Gnorski succeeded J. Michael Hall in the $30,000-a-year slot from which he helps exercise line-item control over the city's $1.4 billion budget.

Gnorski learned the ropes from Hall, who was far more zealous than either Miconi or Silsby in questioning city affairs. According to numerous city employes, Hall flooded them with telephone calls, callenging actions he had read about in the paper or picked up from a critic of the city government.

Even today, according to an insider at the District Building, the Barry administration always tries to anticipate what the reaction on the Hill will be to its actions. For example, if a city contract is awarded to a local minority firm, officials brace themselves for the possibility that a losing bidder may protest to his home state congressman, initiating a flap that could result in budget cuts.

District Budget Director Mack, who deals with Gnorski and Miconi almost daily, said she has detected "no particular bias against the District" from them.

"But their authority is reality," she said. It would be "naive to be surprised" by phone calls and letters from the Hill, she said.

"While we certainly don't agree with all their positions, they take their jobs seriously and operate in good faith, and we respond in kind," Mack said. "This latest flap won't destroy the relationship we have."

Gnorski agrees. "This is not a sign of strained relations with the mayor, but just a reminder of congressional prerogatives."

Mack said she will "continue to operate on two fronts: to make the most of what we have [under limited home rule] and to get what we deserve, which is full home rule."