Right-wing challenger Jeffrey Bell awaits his June 6 Republican primary in New Jersey against heavily favored liberal Sen. Clifford Case with diminished hope for 11th-hour help from his mentor, Ronald Reagan - a fact with broad implications in 1980 presidential politics.

Bell's political intimates still cannot believe that Reagan will keep his back turned on his former idea man and speechwriter. But that is precisely what Reagan's most important advisers tell him is essential to consolidate his position within the party as Republican rather than a conservative ideologue.

Reagan's New Jersey neutrality fits the new policy of non'belligerency toward Republican liberals. Enthusiastic about trying again for president, Reagan covets the role of party unifier in contrast to his unavoidable party-splitting role of 1976. The danger is that, while appeasing his liberal enemies, Reagan may weaken his conservative base.

Reagan has always been ambivalent about party unity. While preaching the 11th commandment, prohibiting one Republican from speaking ill of another, he challenged and badly wounded an incumbent president.

The ambivalence showed through during a swing through the East last December. On Dec. 15, in a television interview taped with us for RKO-General, he urged Republicans to stop "giving each other political saliva tests . . . to find out the degree of our Republican purity."

But two days later when asked over WJZ-TV in Baltimore whether the party should avoid challenging a liberal such as Maryland's Sen. Charles Mathias in the 1980 primary, Reagan replied, "Oh, no." He then hinted that Mathias might well consider switching parties, just as Reagan long ago decided to leave the Democrats. "I'd like to have a talk with him," Reagan said.

Mathias took him up on it during a speaking engagement in California a month later. Reagan invited him to his house at Pacific Palisades, where on Jan. 18 Reagan, his wife and Mathias had a pleasant visit and political conversation. There was no talk of primary challenges or party switching. That pleasant chat in California was the first reflection of determination by influential Reagan insiders that his next presidential push should be less abrasive than his last.

That became clear about six weeks later when the executive committee of the Reaganite Citizens for the Republic (CFR) convened in Los Angeles. The question at issue: Should CFR contribute to 34-year-old ex-Reagan aide Bell's campaign against Case, a 74-year-old symbol of East Coast liberal Republicanism?

Reagan advisers Lyn Nofziger, who personally contributed $50 to Bell, and John Sears argued that both CFR and Reagan should back Bell (who gained notority in 1975 as author of the ill-fated Reagan scheme to cut domestic federal spending by $90 billion). But Nevada Sen. Paul Laxalt, Reagan's 1976 campaign chairman, argued that CFR had been set up on the premise that it would not go "head-hunting" against incumbent Republicans.

The prestigious Laxalt easily carried the day, but deeper considerations were at work. Reagan aides Mike Deaver and Pete Hannaford have long wanted to broaden his appeal within the party (and, for that reason, were not enthusiastic about his campaign against the Panama Canal treaties).

Despite criticism of Reagan's neutrality by the right-wing weekly "Human Events," his staff says only "about five" critical letters have been received. But that is no true measurement. Grumbling that Reagan, at age 67, is getting out of political touch has been heard among conservatives in the House Republican cloakroom.

How, they ask, can Reagan preach Republican unity after his bold assault against President Ford? What's more, they contend Bell is no fringe candidate but has generated support from such respectable conservatives as former senator James Buckley, former treasury secretary William Simon and Reps. Robert Bauman (Md.), John Ashbrook (Ohio) and Jack Kemp (N.Y.).

Kemp is another former Reagan aide hungrily eyeing a Senate seat now held by a liberal Republican (Jacob Javits, whose present term ends in 1980). Closely allied with Bell in a national tax'reduction movement endorsed by Reagan, Kemp went to Milburn, N.J., May 7 to address a Bell fundraiser. While there, Kemp discussed with Bell his intention of telephoning Reagan for a final try to win his endorsement.

To turn down Jack Kemp's last eloquent plea on behalf of Jeff Bell will tax Reagan's toughness. Yet, key advisers tell him he must do so to cool off Republican passions for two years hence. Whether Reagan listens to his head or his heart in 1978 may preview the campaign he can wage in 1980.