When Linda Gregg, a Safeway forklift driver, was elected to the top job in the largest Teamsters union local in Colorado last December, her win marked the biggest victory ever for the dissident group, Teamsters for a Democratic Union (TDU).

Her victory, challenged on procedural grounds by James Ivey, the defeated incumbent, was upheld in January by a unanimous vote of the Teamsters Joint Council, the union's regional governing body.

But Presser and the executive board of the 1.8 million-member union have thrown out the election results and ordered a new vote, prompting charges by Gregg and the TDU yesterday that Presser had "stolen" the election.

"I won the election fair and square, by the rules that were set up by the incumbent," said Gregg, 30, an executive board member of the TDU. She said Ivey appealed the mail-ballot election on grounds that union members did not have adequate time to vote, but said Ivey himself had been in charge of setting up those rules.

Teamsters spokesman Duke Zeller said that the executive board overturned the election April 11 following a review of evidence that showed that more than 200 union members claimed they did not receive ballots in time to vote. Gregg won by 47 ballots among the 4,100 union members of Local 435, the largest local in the union's four-state Rocky Mountain district.

TDU, a Detroit-based group claiming about 5,000 members, has vigorously campaigned for the ouster of Presser and other union officials, alleging that they have run the union in an undemocratic and corrupt fashion.

Gregg had campaigned for secretary-treasurer by charging that Ivey had promoted concessionary contracts. She also strongly criticized Presser and other officials in campaign literature. Ivey could not be reached for comment.

Gregg said she plans to campaign for the office again.