FOR THE PAST several months, the conventional wisdom among reputedly knowledgeable political columnists has been that Senator George McGovern probably won't win the Democratic nomination for President because he is unacceptable to the big city and labor leaders who form the nucleus of traditional Democratic party power. Columnists like Rowland Evans and Robert Novak, Stewart Alsop, and James Reston have consistently passed along the information that Democratic powers like Chicago Mayor Richard Daley and AFL-CIO President George Meany cannot support McGovern's candidacy. They have, however, rarely been able to quote sources to back up their claims.

A spot check with several labor and party officials last week revealed that the conventional wisdom may once again prove wrong.

In Chicago, Mike Neigoff, a spokesman for Mayor Daley, said Friday that "no one has ever quoted Mayor Daley saying whom he supports or doesn't support. At the convention, the Illinois delegation will caucus and hear from anyone who wants to speak to them and then determine who to support." This isn't saying much but it's far from proclaiming McGovern's unacceptability.

In Washington, Albert J. Zack, the Director of Public Relations for the AFL-CIO and a spokesman for George Meany, said Friday that the nation's largest labor organization is taking no position "except that we are absolutely opposed to George Wallace and we will fight him." Zack added that Meany himself will be "neutral until after both conventions."

SIMILARLY, the United Auto Workers Union finds McGovern far from odious. An article in the Detroit Free Press last Friday reported that United Auto Workers Vice President Olga Madar recently spoke in McGovern's behalf at a reception for Victor Reuther, retired UAW official and backer of the Senator. She said that UAW Vice Presidents Douglas Fraser and Irving Bluestone and Secretary-Treasurer Emil Mazey "will be in there actively compaigning" for McGovern.

Joseph Crangle, chairman of the Democratic Party in New York State, is staying neutral in the Presidential race until after the Empire State's June 20th Primary. He feels, however, that McGovern would have "no problem in getting support from the so-called regular organization." Of the assumption that McGovern could not get regular support, he said. "It seems to be a premise fostered by people who aren't entranced with McGovern's candidacy." Crangle added that "feelings are not the same in 1972 as they were in 1968. McGovern doesn't cause people to feel short. He's not an individual they (the regulars) feel they cannot work with." And in Philadelphia, a spokesman for Philadelphia Democratic leader Peter J. Camiel, who supported Muskie, said Friday that "every candidate is acceptable." What the "establishment" columnists don't mention (and should and probably do realize) is that organization politicians aren't particularly concerned with ideology. Their main concern is with winning, and if McGovern looks like a winner, they'll support him.

Regular Democrats like Matthew Troy, Queens Democratic County Leader in New York City; Sebastian Leone, Borough President of Brooklyn and a confidante of Brooklyn County Leader Meade Esposito; and Arthur Barbieri, chairman of the Democratic organization in New Haven, are all supporting McGovern. They are doing so for their own reasons, which frequently have a lot to do with party infighting in their own areas. But the very fact that they have gone with the Prairie Senator contradicts the thesis of the establishment columnists.

OF COURSE, the experience of the Muskie campaign shows that these party leaders cannot always produce votes to go with their endorsements, and no one is claiming that neutral leaders like Daley and Meany will not support McGovern at the convention. The point is that McGovern is certainly not anathema to party leaders, as some columnists claim.

Maybe the inside dopesters have contacts the rest of us don't. Maybe they know more about what Mayor Daley is thinking than we do. No one can judge that. What we all can judge is their record: the prediction of a centrist "Real Majority," the dismissal of McGovern as "not a serious candidate," and the claim that Muskie was unstoppable as long as he didn't move too far left. Looking at these things, and at the evidence piling up against their latest reports of McGovern's unacceptability to Democratic regulars, one begins to suspect that the knowledgeable columnists are not so knowledgeable after all; that they are not so much reporters of fact as they are voices for conservative Democratic hopes.