Cambridge City Councillor Marjorie C. Decker withdrew her candidacy for the Mass. State Senate yesterday, saying that her chances of winning the seat were too slim to justify continuing her campaign.

“When the Special Election for State Senate was first announced, I considered the prospects for victory extremely promising,” Decker wrote in a statement. “Since I announced my candidacy, the number of candidates has increased dramatically—more than doubling—thus my chances of winning have been greatly reduced. In good conscience, I cannot ask my family, friends and supporters to give more time, effort and financial support if there is no realistic prospect of success.”

A special election for the Middlesex, Suffolk, and Essex State Senate seat will be held on May 11. The seat was vacated in January when former Senator Anthony D. Galluccio was imprisoned for an alcohol-related probation violation. While the ballot for the special election will not be finalized until next Wednesday, as many as ten candidates may be seeking the seat.

Decker’s campaign Manager Jeni M. Wheeler said that “Marjorie does not back down from a fight,” pointing to her exhaustive write-in campaign that won her a sixth term on the City Council in November. Decker had failed to file her paperwork in time for her name to appear on the ballot.

But Wheeler said that Decker and her campaign team concluded this weekend that it is “nearly impossible for anyone but the Everett candidate to win” the seat. She noted that Everett has historically produced 40 percent of the voters in special elections for the district—and Sal DiDomenico, Galluccio’s chief of staff, is the sole candidate from Everett.

Furthermore, Wheeler predicted that the 20 percent of the electorate that typically hails from Cambridge will split its votes among the three remaining Cambridge candidates—Dennis A. Benzan, Timothy R. Flaherty, and City Councillor E. Denise Simmons.

But Flaherty’s campaign is not simply counting on Cambridge voters, according to Flaherty’s media consultant Dorie R. Clark, a graduate of Harvard Divinity School.

“We’re definitely not relying solely on one city for a preponderance of votes or our campaigning,” Clark said. “We feel very fortunate that our campaign has the funding and the broadbased support of a varity of organizations.”

In addition to Cambridge and Everett, the contested district includes Allston, Brighton, Charlestown, Chelsea, Revere, Saugus, and Somerville.

—Staff writer Julie M. Zauzmer can be reached at jzauzmer@college.harvard.edu.