In the past 46 years, the 16th Congressional District of Illinois has changed representatives exactly once. That was back in 1960, when Rep. Leo Allen (R) retired after 28 years and was succeeded by Rep. John B. Anderson (R) who has held the seat ever since.

Despite the security that would seem to go with the job, "John B." as he is known here, is running scared.

It's not the Democrats who did it, despite the fact that the once-scorned minority party has come far enough to elect the mayor of Rockford and win half the seats on he Winnebago County beard.

Rather, it is conservative minister, Donald M. Lyon, whose challenge in the March 21 Republican primary has Anderson worried.

The contest has drawn national attention because Anderson, third-ranking in the House Republican leadership, is the most prominent target for the much-publicized "New Right" effort to eliminate or intimidate liberal Republicans.

"I don't think I'm being paranoid," Anderson said the other night, "when I say that I'm the test case for this whole effort to purge the Republican Party of any progressive element. Mine is an early primary, and if they defeat the chairman of the House Republican Conference, they can put the fear of God into a lot of other Republicans."

When Anderson says "they" are doing this, he is not referring to the handful of prominent local businessmen, the right-to-life activists, the gun-club members of Lyon's former parishioners in the fundamentalist Open Bible Church who comprise the backbone of the challenger's campaign organization.

Rather, he means the network of conservative political action groups based in Whashington, which employ electronic mailing-lists to tap the wallets of conservative true-believers all across the country and use the proceeds to finance and staff the campaigns of right-thinking candidates in targeted races.

It is these organizations - many of them serviced by direct-mail expert Richard Viguerie - that are credented with putting new muscle into the conservative movement in this country.

They have been trumpeting the Lyon-Anderson clash in their publications and were instrumental in bringing together the novice candidate and an experienced campaign manager.

But oddly, the conservative organizations have yet to give their first dollar to the Lyon campaign.

And, contrary to the impression in Washington, there are key Republicans here who say that to the extent Anderson has any real problems with renomination, they have less to do with a resurgence of conservatism than with the age-old complaints about the secure incumbent who neglects to keep his political fences mended.

Thus, the Anderson-Lyon contest, rather than being a straightforward test of the conservative movement, is more complicated, showing both the strengths and the weaknesses of this emergent political force.

Consider, for example, the cross-pressures on one of the conservative groups the Committee for the Survival of a Free Congress. The CSFC's director. Paul M. Weyrich is one of the best-regarded profesionals in the movement and its $757,000 in receipts last year put it near the top of conservative groups in affluence.

Lyon met Weyrich soon after he decided to run and a CSFC field man. John Proctor, was assisted to monitor the campaign. At CSFC-sponsored candidates' school in Milwaukee, Lyon was brought together with 26-year-old Britt Beemer, an experienced congressional aide, campaign manager and former CSFC staff member, who agreed to take over the Lyon campaign.

Despite this strong involvement, CSFC has yet to commit any funds or staff to the campaing. Weyrich says Lyon's effort "does not yet meet our criteria for organization competence and there's no sense putting money in unless it's a do-able situation."

But he also acknowledges that even a hint that the group might back a challenge to Anderson brought sharp controversy among its conservative congressional sponsor.

When a Washington column reported erroneously last fall that CSFC was already backing Lyon, the congressional sponsors - whose names lend credibility to the organization - called in Weyrich for a meeting According to Rep. Thomas M. Kindness (R-Ohio), they split almost evenly on the wisdom of backing Lyon. But one of those who opposed it. Rep. E. G. (Bud) Shauste (R-p), felt so strongly that he quit the advisory board anyway.

Shuster, a staunch conservative, said in an interview, "I disagree with John Anderson often, and some days I wish he wasn't there. But he is an outstanding member of Congress and he represents the Republican point of view on most issues. To challenge him would just be to impale the Republican Pary on one more useless skewer."

Other conservatives accuse Shuster of ideological deviationism for putting the interest of the Republican party over those of the movement. But CSFC is not the only group immobilized in the Lyon-Anderson campaign by such objections. The Conservative Victory Fund of the American Conservation Union has also been blocked from making a contribution by objections from Reps. Robin Beard (R-Tenn.) and Edward Derwinski (R-Ill).

That does not mean Lyon has been abandoned. The National Conservative Political Action Committee (NCPAC), whose executive director, Terry Dolan, says it avoids having congressional sponsors "just so we won't be subject to the buddy-system," is loaning Lyon $5,000 and later may make a direct contribution.

Dolan said the $5,000 will be used to finance a mailing by Viguerie to a national list of conservative givers. The proceeds of that mailing - after Viguene's costs have been paid - will be used too finance a direct mailing for Lyon into the 16th District.

Meantime, however, the Lyon campaign - bannered as the year's most significant challenge to a sitting congressman - is limping along on a meager financial ration. Through the end of the year it had raised $35,600 and was $9,000 in debt, while Anderson the beneficiary of fund-raising apperances by former President Ford and former Secretary of State Kissinger, had a campaign balance of abot $30,000.

But that disparity has not inhibited Lyon from indicting Anderson, at every available forum, for allegedly "failing to represent this district." He has criticized Anderson's positions - and the incumbent says, sometimes distorted them - on the Panama Canal treaties, gun registration, abortion, busing foreign aid, assistance to New York, food stamps and funds for the B-1 bomber. "He was a conservative when he got elected," say Lyon, "but he's changed now, and he comes back here talking like some godd of the East."

That charge is echoed in various forms by other Anderson critics. Business Roger Proctor is backing Lyon because, although he graduated from high school with Anderson and has been a friend for 40 years, he thinks "some one has led him down the garden path in Washington. He's not a man of the people any more : he doesn't represent Midwest thinking.

Despite such criticism, Anderson maintains the support of most of Rockford's politic-economic establishment, of the local press and privately - of many Democcrats as well. "If I thought there was any chance of Jobn B. getting licked," said one leading local demoncratic official, I'd have my wife vote in the Republican primary. I can't cross over myself, but I'd ask her to, because we can't afford to lose that man."

His comment reflects the prestige Anderson also enjoys in Washington - where his early advocacy of civil rights, his leadership in House reform efforts, his break with Richard Nixon on Wategate and his oratoncal eloquence have made him the object of occasional presidential or vice presidential boomlets.

But far beyond conservative circles here, a feeling exists that John Anderson has lost some touch with home. More than a year ago, Kiki Anderson, the congressman's wife, began to "hear those vibrations," and decided it was time for her and their children to move back to Rockford.

Anderson himself has been coming back almost every weekend since then, but occasionally he seems forgetful of where he is. In a town meeting the other night in Freeport, he delivered a 35-minuta review of issues before Congress, then slapped his head in chagrin at the first questioner's reminder that he had said nothing about farm problems. "I didn't mean to overlook that," Anderson said.

Beemer, the Lyon campaign manager, tell of a youth from one of the rural counties in the district who went off to Harvard and reported to his parents. "I've seen our congressman a lot more often at the Kennedy Institute up here than I ever did at home."

Beemer also said that if Lyon should defeat Anderson. "I don't think it would be a national trendsetter." So far only two other prominent liberal Republicans. Sens. Clifford P. Case (N.J.) and Edward W. Brooke (Mass). have conservative challengers in their primaries, and Brooke's is not a certainty.

"More then reflecting a resurgent conservative movement," Beemer said, "it would show any incumbent, Republican or Democrat, that if you stay away too long you can be in trouble."

But few people believe, at this point, that Anderson will be beaten. Weyrich said his estimate is that if the election were held now - and not eight weks from now - Lyon would do well to get 35 per cent of the vote.

A courthouse Republican, supporting Anderson, said that prediction could under estimate Lyon, because the minister "will draw in people who have never been in Republican politics before - some farmers, some conservative blue-collar Democrats, some of the fundamentalist church people, the strong right-to-life people."

But even this official said the only way Anderson could lose "would be if he overreacts to the challenge. John B. isn't used to having an opponent, and he's pretty uptight about it. He's been running around trying to get people to put up lawn sign for him, just because Lyon is doing it. Well, hell, Lyon needs name identification: John B doesn't. And it's pretty hard to keep a lawn sign up in the middle of a Rockford winter."

But to some of those in the conservative movement, March 21 is the beginning, not the end, of their effort to discipline John Anderson. Dolan, the NCPAC director, said, "The Don Lyon campaign is Round One. John Anderson is wrong on too many issues ever to have a free ride again. He may get away with it this time, but he won't get away with it forever. Sooner or later, he's going to have to decide whether he wants to give up some of his so-called principles or give up the seat from that district."