T.S. Eliot once wrote that "April is the cruelest month," but what did he know about running for president? For the candidates for the Democratic nomination for president, July might be worse.

July has blossomed into constituency month. Over the next four weeks, the Democratic candidates are taking their caravan to gatherings of teachers, Hispanics, environmentalists, women, blacks, senior citizens and--twice--party officials.

The candidates see these gatherings as an opportunity to make inroads with political activists who will be important in the caucuses and primaries of 1984.

But in running this gauntlet, the Democrats inevitably will reinforce the idea that their party is little more than a collection of constituencies competing for their own interests.

This in turn will stoke the criticism that the party's presidential candidates weaken themselves for the general election by not being perceived as viewing the electorate as a unified whole.

It is a month, said Mike Fernandez, press secretary to Sen. Ernest F. Hollings (D-S.C.), "of fulfilling everybody else's dreams."

The courtship began Thursday in Philadelphia at the National Education Association (NEA) convention, where candidates were prohibited from speaking directly to the full convention and instead addressed the delegates by video tape. Like salesmen at other conventions, the candidates had booths for hawking their wares and were allowed to court the teachers at smaller gatherings.

At the same time candidates were shuttling to Detroit for the annual meeting of the League of United Latin American Citizens (LULAC), the oldest and largest Hispanic group in the country.

On Saturday, the scene shifted to Aspen, Colo., for a forum sponsored by the Sierra Club.

On July 10, the candidates will travel to San Antonio to speak to the National Women's Political Caucus.

The following week, they will hopscotch to New Orleans for the annual meeting of the NAACP and to Detroit again for a meeting of the Democratic National Committee.

On July 20, the candidates will appear before the National Council of Senior Citizens at a forum moderated by Rep. Claude Pepper (D-Fla.).

During this time, the candidates will appear in pairs on successive Wednesdays before the House Democratic Caucus, which will have 164 delegates to the Democratic National Convention next year. One of the questions the caucus has asked the candidates is:

"Questions have been raised in the press about the extent to which the Democratic nomination process is influenced by the endorsements of specialized constituencies and interest groups. Do you think that what it takes to be nominated is at odds with what it takes to win in the general election?"

Not all the candidates will attend all gatherings. Sen. Alan Cranston (D-Calif.), Sen. Gary Hart (D-Colo.) and Hollings are expected at all eight stops. Sen. John Glenn (D-Ohio), who has pursued a somewhat more independent approach to the campaign, was not in Aspen and may also miss the meeting with the senior citizens. Former Florida Gov. Reubin Askew is a question mark at the NWPC.

Meanwhile, former vice president Walter F. Mondale, the candidate most criticized for being too close to constituency groups, missed meeting with environmentalists and almost missed seeing the women and the NAACP.

Just before leaving for a fishing vacation in northern Minnesota, Mondale decided to go to San Antonio and New Orleans after all.

Even before that Mondale had been forced to do some artful juggling of schedules. Mondale originally had planned to spend parts of three days in Philadelphia courting the teachers, who are expected to endorse his candidacy later this year and are a valuable source of campaign workers.

That meant he would have missed the meeting of LULAC, whose members may be no less committed to Mondale than are the teachers, but whose record of activism in party caucuses and primaries does not match that of the NEA.

But Tony Bonilla, LULAC's president and a closet Mondale supporter, intervened. He said last week it was "major mistake" for Mondale to skip the LULAC meeting. On Wednesday, Mondale's office announced that the former vice president would stop there briefly en route from Philadelphia to his vacation.

That is the clearest example of what an official for one campaign described as the constituencies "flexing their muscles" this month in bidding for the candidates.

The candidates reportedly see it as a mixed blessing.

"To a certain extent it diverts you from spending time in targeted states," said one press secretary.

He added, however, that there are obvious benefits. "These are people who are going to go back and work in the campaigns. It's a good vehicle for the candidate to have all the activists in one place. The activists will play more of a role this time than last."

But their are worries that some of the sponsoring organizations may be flexing their muscles more for their own interests than for the good of the nation. A number of these groups are trying to encourage their members to participate in the delegate-selection process next year and believe that the appearance of the candidates will stimulate more activity.

And as Polly Freeman of the Sierra Club said, the fact that four Democratic candidates were to appear in Aspen Saturday would "make the whole weekend a more exciting event."

So, while Eliot didn't know much about the cruelties of summer, he may have understood constituency politics.

"There will be time," he wrote in another context, "there will be time/ to prepare a face to meet the faces that you meet . . . / And time for all the works and days of hands/ that lift and drop a question on your plate."