John Anderson's 20-year journey from Goldwaterish young congressman to trendy presidential candidate neared its destination the evening of Jan. 10 in a posh Manhattan apartment when he received from multimillionaire General Motors heir Stewart Mott the maximum $1,000 check for his campaign.

Mott, a left-of-center activist renowned for lavish politial contributions in pre-$1,000-limit days, had singled out Anderson as his favorite Republican running for president. So had other liberals crowding into the East Side apartment for the fund-raiser, as well as their West Coast counterparts at a Beverly Hills reception a week later.

Anderson vaulted from obscurity following the televised Republican candidates' debate in Des Moines Jan. 5, but not so much as the candidate of the desiccated Republican left as of the frustrated Democratic left. Since liberal Democrats can advance his empty prospects for the Republican nomination not one inch, Andersnon's burst of acclaim underlines that the new ideological polarization of the two parties makes him an anachronism.

In the debate, Anderson displayed the tough articulation that has won admirers in Congress for two decades. So non-liberal a critic as William F. Buckley's National Review praised Anderson's courageous support of the grain embargo, in contrast to his pusillanimous rivals. But national praise for Anderson -- which we heard all over Iowa the week after the debate -- came from newsmen and Democrats.

That was proved by Iowa Republicans, who in the Des Moines Register poll gave him only 1 percent support for president and, more revealing, rated him a loser in the debate. What the Democrats and editorialists found so attractive in Anderson was that he sounded so much like a Democrat. While his party presents a united front on tax reduction and a tough foreign policy, Anderson dissents on both.

Only 35 people had expressed pre-debate interest in the Jan. 10 Manhattan fund-raiser, but over 200 showed up (requiring two sittings). The Jan. 20 West Coast affair generated so much interest it was moved from millionaire Stanley Sheinbaum's home to the Beverly Wilshire Hotel.

Sheinbaum is no less a leftist activist in Los Angeles than Mott is in New York. But whereas Mott also backs Sen. Edward Kennedy for president, Sheinbaum is only for Anderson. Describing himself to us as a latter-day Diogenes "looking for a thinking man," Sheinbaum wrung his hands in despair over President Carter and disappointment with Kennedy before finding Anderson.

He is not alone. Sheinbaum's co-hosts in the Anderson fund-raiser were Norman Lear and Grant Tinker, socially conscious Hollywood liberals famed for television production but not for fraternizing with Republicans.

This hardly could have been expected by the magnetic Rockford, Ill., lawyer who entered Congress in 1961 at age 38. His liberal rating, as measured by the Americans for Democratic Action, for the first three years was zero. In 1964 (when he ducked a visit to his home district by that ferocious Eastern liberal Nelson Rockefeller), Anderson's ADA rating rose to 7.7 percent. In 1966, it subsided back to zero.

His votes began to change in the late 1960s. In 1978, Anderson voted the liberal line 64.7 percent of the time; but if he had been present for all ADA-selected roll-call votes, his percentage would have surpassed 70 percent -- extraordinary for a Republican, but exceptional even for a Democrat these days.

Apart from percentages, Anderson's appeal to the Motts and Sheinbaums is framed in his national security positions: against the B1 bomber, against the MX mobile missile, against a nuclear-powered carrier, against Carter's proposed 5 percent defense spending boost. Although his unmatched oratory held the House spellbound Aug. 10, 1978, when he called for the Kemp-Roth 30 percent tax reduction, this tie to regular Republicanism was strictly vestigial: Anderson now opposes Kemp-Roth.

That irritates Rep. Jack Kemp, who braved disdain from fellow conservatives to campaign for Anderson in 1978 against a right-wing congressional primary foe. But it was not Kemp who saved him. The United Auto Workers, helped by many Democratic precinct chairmen, ran a re-registration campaign to bring Democrats into the Republican fold. The difficulty of duplicating this re-registration feat in a presidential election year, an initmate of Anderson told us, in one reason he is running for president instead of Congress.

Re-registration of Democrats is the heart of Anderson's campaign for president, particularly in Massachusetts. While he claims this broadens the base of the Grand Old Party, that rests on the premise that the nominees of both parties ought to be similar in their ideology. That might have been arguable a dozen years ago when there was a broad national consensus on major ideological issues. Instead, the new interest in John Anderson looks like a desire by disenchanted Democrats for not one but two Democratic nominees.