At his home in Palm Springs within the next 30 days, Gerald R. Ford will get this hard word from professional political advisers: If you want to be president again and if you want to keep Ronald Reagan from being nominated, you must become an active candidate -- and soon.

That means running in the primaries, not waiting at the 19th hole for a plea from the Republican Party. Ford's advisers will not recommend, only lay out options and probabilities: if he opens a campaign during the next two months, perhaps 50-50; if he awaits a draft, forget it.

Such blunt talk is intended to dispel the unrealistic aura developed around Ford by sycophants, especially former and present staffers. Ford has told friends that "you won't see me plowing through the snows of New Hampshire this time; yet he passionately wants to get back in the White House -- ar at least keep Reagan out. At the forthcoming secret meeting in Palm Springs, he will be told he cannot have it both ways.

The need for Ford to face reality has been hastened by two interrelated developments. The first is that no active candidate has been able to break out of the pack against the front-running Reagan. The opinion of Ford's advisers that only the 'former president can stop Reagan is widely shared by influential Republican leaders.

The second is Sen. Edward Kennedy's prospect as the most likely Democratic nominee. Since the polls show Reagan beating President Carter but losing badly to Kennedy, the quest for an alternative has taken on new life.

The advent of Kennedy had nothing to do with making Jerry Ford the charter member of the anybody-but-Reagan club. Within weeks after leaving office in 1977, he confided he might run again if it appeared Reagan would be nominated by default. Despite Reagan's peacemaking efforts, Ford's bitter language in his memoirs ("his [Reagan's] problems") shows that he still believes the 1976 Reagan challenge made Jimmy Carter president.

But Ford has not spent the years out of power as an articulate voice carving out an opposition record. Instead, he has divided his time between the golf course and the lucrative podium, with scant time for politics. While Kennedy and other major figures addressed the National Urban League convention at Chicago in late July, Ford was in the city talking to the Laundry and Dry Cleaning Institute's convention about Carter's Cabinet shake-up.

Passing up the Urban League for the dry cleaners is blamed by Ford's political supporters on his executive assistant, Maj. Robert E. Barrett. A young infantry officer serving as President Ford's Army aide, Barrett resigned from the service after the 1976 election to go with the defeated candidate to Palm Springs. Since then, he has become Ford's most intimate adviser.

Like his boss, Barrett is unaware that primaries obviate a brokered convention. Consequently, he has told politicians, newsmen and Ford himself that the Detroit convention will turn to the former president. Several of Ford's exstaffers, possibly unenthusiastic about getting inducted into another relentless primary chase against Reagan, echo Barrett.

Many prominent Ford-for-president enthusiasts, such as Vermont's Gov. Richard Snelling, want him to run in the primaries but believe, against all evidence, that he can be nominated even if he does not. It will be the mission of the political pros at Palm Springs to persuade Ford that this is pure nonsense.

One such adviser will inform Ford that, to return to the White House in 1981, he must endure those New Hampshire snows in 1980. The Boston Globe poll giving Ford an edge over Reagan among New Hampshire Republicans (who overwhelmingly favor Reagan over anybody else) convinced this insider.

While fund-raising would prove difficult this late and Ford's lackadaisical performance since 1976 has soured some erstwhile supporters, he could easily assemble a campaign organization. Key professionals in his 1976 campaign -- Stu Spencer, Bob Teeter and John Deardourff have not joined any other campaign.

Some other prominent Republicans who would not join Ford still hope he decides to run; they reason that a renewed Reagan-Ford battle could unlock the process and open support for a third candidate. Jerry Ford's political advisers are not the only Republicans who believe the alternative to his active candidacy is a Kennedy-v.-Reagan race that they fervently want to avoid.