When Rep. Frank A. LoBiondo (R-N.J.) was campaigning for a second term last fall in his sprawling district in southern New Jersey, he left the running of his congressional office back in Washington to his chief of staff and turned to a paid political consultant to help with his campaign up north.

It was an easy decision made easier by the fact that the consultant and the chief of staff were the same person: LoBiondo's longtime close aide and adviser, Mary Annie Harper. From August until November, Harper drew a partial government salary while her Bridgeton, N.J., consulting company, Harper Associates, was paid $11,250 out of LoBiondo campaign funds. In addition, Harper's 73-year-old mother received between $500 and $1,000 a month from the campaign.

Harper's involvement in her boss's reelection effort while serving in a taxpayer-funded government job illustrates how blurred the line between politics and official duties in Congress can be.

GOP leaders have chastised President Clinton for dragging politics into the White House to an unprecedented degree, and they have criticized Vice President Gore for soliciting campaign contributions by telephone from his office. But on Capitol Hill, walking the fine line between money and politics has been refined to a high art.

To an extent that would be un thinkable in the executive branch, political activity is entrenched in the culture of Congress. Ethics rules permit congressional staff members to engage in partisan political activities -- as long as they do not use government resources and have completed their official duties before they begin dialing for dollars.

The way the rules are written and interpreted, hundreds of congressional employees perform political work from writing campaign speeches to soliciting contributions -- and it's all legal. Senior staff members can mingle with lobbyists at Washington fund-raising events at which political action committees fork over checks to their boss. Others take a leave of absence or use vacation time to join the boss's campaign in election years.

"While a lot of the staff people are technocrats, they all catch on fairly quickly that if they don't work hard for their bosses and be sensitive to financing, among other things, they might not have a job for long" because their boss would lose, said former senator Paul Simon (D-Ill.).

Both parties have devised elaborate systems to avoid the appearance of abuse. Senators and House members, sometimes accompanied by staff members, hustle over to their respective party headquarters on Capitol Hill to make campaign calls from "private" turf. Some don't even bother to walk the few blocks from the Capitol. Instead, they just step outside to the parking lot and use cellular phones to avoid using official lines.

For his last run for office in 1990, Simon rented a one-room office with a phone on Massachusetts Avenue. A former aide to a House member told of using the office of a lobbyist based near the Capitol -- a fairly common practice, according to other sources.

Recent disclosures suggest that abuses may still occur, however. Roll Call newspaper reported last month that Rep. Dan Burton (R-Ind.), who heads a congressional investigation into Democratic fund-raising abuses, was in his congressional office when he discussed fund-raising matters with lobbyist Mark A. Siegel, a Democrat, in 1995 and 1996. A spokesman denied that Burton had ever solicited funds from his office.

A Republican committee chairman who recently telephoned a lobbyist to discuss a fund-raising event was whispering, and the lobbyist asked why. The chairman explained he was calling from a committee hearing, implying he was using a government line, according to a congressional source who would not identify the chairman.

Over the years, Congress has steadily tightened ethics rules and expanded disclosure requirements for members and staff. A law dating to the 1970s bars Senate aides from handling campaign contributions, except for three designated members of each office. Rules such as that addressed some of the blatant abuses in years past, a freer and easier time in which one former House member, Frank Clark (D-Pa.), was indicted for placing 11 campaign workers on his congressional payroll and pleaded guilty to related charges.

But the rules still appear to permit a wide range of practices that, while permissible, may not seem proper or appropriate to some members of the public.

"The constraints on what you can and can't do are well spelled out. It's the issue of perception that is trickier," said Douglas D. Ritter Jr., chief of staff for Rep. Curt Weldon (R-Pa.) and vice president of the Association of Administrative Assistants.

Until the House amended the rule in January, it was permissible, for example, for a House GOP leader to hand out campaign checks from tobacco lobbyists to other members on the House floor.

The Washington Post has reported that a House Commerce Committee staff member who helped draft 1996 legislation relaxing regulation of the securities industry sounded out several securities firms about donating $100,000 to the Republican Party last October. The calls were made from a non-official line at the National Republican Congressional Committee, the chief political arm of the House GOP, and may not have violated any House rules. But the committee's chief of staff ordered the calls stopped after learning of the approaches.

American University professor James Thurber says there is a "seamless web between campaign managers and lobbyists." And many top congressional aides now serve as managers or overseers of campaigns, making it difficult at times to avoid conflicts.

Even when the chief of staff doesn't make fund-raising calls, "there's a perception that he needs to know something about these efforts and be supportive of them," said Richard Shapiro, executive director of the Congressional Management Foundation, a private organization.

That is not new, Capitol Hill sources say. Congressional staffs, almost by definition, are run by people with political experience that often includes a fund-raising background.

Biographies of chiefs of staff in the House and Senate show they have worked in a host of campaign-related functions, including teaching in campaign academies, consulting for the National Republican Congressional Committee, and serving on political action committees for lobbying groups and trade associations. Terry A. Carmack, chief of staff to Rep. Anne Northup (R-Ky.), is a former chairman of the Kentucky Republican Party.

"You always want someone in that job who is in close touch with your constituents," said former senator Sam Nunn (D-Ga.). "You really have to have somebody who is politically astute."

For LoBiondo, that bill has been filled by Harper ever since LoBiondo served as a county official in New Jersey more than 10 years ago, and through his subsequent service in the state Assembly before being elected to Congress on a second try in 1994.

For Harper, that has meant wearing two hats since she started her campaign consulting firm in 1991. In 1993 and 1994, Harper Associates was paid thousands of dollars by Christine Todd Whitman's gubernatorial campaign, the New Jersey Republican State Committee and the LoBiondo campaign. The firm also drew a small salary from the state of New Jersey while serving LoBiondo in the Assembly, according to Harper's financial disclosure report.

When LoBiondo defeated Democrat Louis Magazzu for the congressional seat in 1994, three other campaign workers besides Harper went to work on LoBiondo's congressional payroll: Steven W. Wilson was press secretary, Jennifer B. Leslie became a legislative aide and Richard van Noord worked in the district office.

Leslie quit the staff last summer to go back to work for the campaign. Wilson and van Noord left for other reasons.

Harper said she began her part-time campaign work in August under an arrangement in which she received slightly less than half her regular salary of about $80,000 a year.

Harper said recently that an attorney at the House Committee on Standards of Official Conduct advised her that the dual roles were proper "as long as you keep the two apart." LoBiondo said he approved the arrangement only after "we made sure we did everything right, and I was satisfied we could separate it."

Harper said she worked in Washington when Congress was in session, then got into her car and headed for New Jersey, carrying mail and other business with her for the district office. Weekends, she said, she worked in LoBiondo's campaign headquarters.

Fund-raising was handled by another consultant, she said, while Harper helped the campaign manager, Sean Spicer, with the "local political landscape. . . . Sometimes it was as basic as how do you get from one town to another."

A New Jersey Democrat said Harper was a constant presence at LoBiondo's side at all events, and added that voters would have been hard-pressed to know whether she was there as campaign adviser or government aide.

That isn't a distinction that LoBiondo has trouble with.

"My chief of staff is someone I rely on for advice on issues, how things come together with different positions I've taken," he said. "In the campaign, her role was to help out with issues and help the campaign manager."

LoBiondo, who had strong support from the National Rifle Association and gambling interests with holdings in the Atlantic City area, was reelected easily. In November, Harper returned to full-time duties as his chief of staff. CAPTION: REP. FRANK A. LoBIONDO