When volunteers for Theodore G. Venetoulis began telephoning the voters Tuesday morning whom they had painstakingly targeted earlier as sure supporters of their candidate, they found that by election day a great many minds had been changed.

"Some said they were voting for Hughes. Others said they weren't sure they would vote for Ted anymore," said Steve Gelobter, coordinator of the volunteer organization upon which Venetoulis had staked his chances for victory.

"As far as I know, our organization worked. We got out the voters, but when they went into the polls a lot of them didn't vote for us," he daid.

By yesterday morning, Gelobter could find some humor in the prospect that Venetoulis volunteers might have ferried voters for the victorious Harry R. Hughes to the polling places. Especially in Baltimore County, where Venetoulis is the county executive, Gelobter said the swing toward Hughes was obvious before the first vote was counted. Even Venetoulis sensed the voters' antagonism toward him on Tuesday.

"I went to some Baltimore County precincts and guys would come up to me and say 'Venetoulis, I'm not going to vote for you." he said. "It was chilling."

By the close of election eve, Venetoulis had picked up only 24.4 percent of the vote in the Democratic primary for Maryland governor, placing him third behind Hughes and Acting Gov. Blair Lee III. It was a poor showing for the man considered Lee's chief rival in the race, and it spelled an interruption if not an end to his career in elected politics.

Venetoulis had a number of theories to explain his loss and Hughes' victory, chief among them were his own weaknesses. "If you're not strong enough to survive the rough spots in a race, then you should not win. I wasn't strong enough."

Venetoulis' whole strategy of raising controversy and making blanket attacks against his opponents created many of the candidate's problems.He tried to cut a figure as a new politician leading a "new Maryland."

For his new alternative, Venetoulis found thousands of volunteers who toiled for weeks in his campaign. But many voters, finally, decided that the candidate had "style without substance."

And Venetoulis, the candidate who jogged through neighborhoods and held press conferences staged before publicity-grabbing settings, said yesterday that he was overexposed. "In the end, I was the one under scrutiny.It was too much. In the last debates I was the target of the three others and Lee's negative ads on the radio," he said.

"I was on the defensive. I think the voters saw Lee and I as too controversial, and they chose Hughes. I don't want to take away from Harry. His was a stunning victory."

Hughes won by ignoring not only traditional political strategy but also the almost textbook campaign waged by Venetoulis.Venetoulis received labor endorsements. He published over a dozen major issue papers. He set what he thought was a low camgaign budget of $500,000.

Hughes' budget was little more than $175,000.

Venetoulis said he may go back to teaching, a career he abandoned in 1971 to take up politics full-time. "Politics is such a tough business . . . I don't think I'm sold on it as a profession."

Walter S. Orlinsky, the fourth-place candidate in the race who won only 4.4 percent of the votes, was more sanguine about the election yesterday, saying he was happy to have lost to Hughes rather than to the others. Orlinsky remains the Baltimore City Council president. His running mate, Ronald Young, goes back to Frederick to be its mayor. Neither had to give up his position to run for statewide office.

Venetoulis, however, had to abandon a reelection race for county executive to run for governor, and Ann Stockett gave up her Anne Arundel County Council seat to run as his lieutenant governor candidate.

"I would rather Harry won than anyone besides me," said Orlinsky, who generally side with Hughes as a fellow underdog in the elections. "I feel I have a good conscience. The only thing I'm worried about is my son, who is not accutomed to seeing his Daddy lose."

Orlinsky said he "called the race from day one - only I didn't have the same winner. I was conviced Ted and Lee weren't popular candidates and that Harry and I were the alternatives. If the Sun papers had leaned towards me, maybe the voters would have seen me as the vehicle which was the best for saying 'to hell with you all' to the old politicans."

Louise Gore, the Republican gubernatorial nominee in 1974 who placed third in Tuesday's GOP primary, had no immediate plans for her postelection life. Although she said she would work for her party's nominee, J. Glenn Beall Jr., she said she thought the voters had already selected a new leader: Harry R. Hughes.