“It’s part of the Democratic process that each candidate who has earned a place on the ballot has an equal opportunity to be heard by voters,’’ Walsh campaign spokeswoman Gabrielle Farrell said in a statement.

The Walsh campaign said it has received debate invitations from almost every major news organization in Boston. But the mayor will not participate in a debate before the preliminary election unless all four contenders on the ballot are on the podium, the campaign said.

The Sept. 26 preliminary election is less than three weeks away, and Mayor Martin J. Walsh has so far not accepted any invitation to debate his main challenger, City Councilor Tito Jackson.


Jackson said he is open to debating the mayor alone or with the other two candidates whose names are on the preliminary ballot.

“I’m not sure what Mayor Walsh is afraid of,’’ said Jackson, who has been on the council for six years. “I’ve asked now tens of times that we have a debate. I believe that we owe it to the people of Boston to have a debate with all the candidates.”

The two other candidates are Robert Cappucci, a former school committee member, and Joseph Wiley, a customer service representative for MassHealth. Both men live in East Boston. Only the top two vote recipients on the Sept. 26 ballot will proceed to the municipal elections in November.

In a Boston Globe/Suffolk University poll released in June, just 1 percent of the respondents said they would vote for Wiley, and fewer than 4 percent said they would vote for Cappucci. Jackson got 23 percent to Walsh’s nearly 54 percent.

In an interview, Cappucci said he worked hard to get his name on the ballot, adding that he submitted 2,400 signatures above the required 3,000 to election officials and spent more than $30,000 of his own money on the campaign. He said his campaign is erecting billboards in five neighborhoods, and he and his volunteers are handing out 200,000 cards on his political views.


“I feel that this is not really nice,’’ Cappucci said about not being invited to the debates. “It’s just not the way the American democracy system works. . . . I deserve to participate.’’

He said he has contacted or tried to reach at least four organizations, including the Globe, but has no word on whether he is invited. Wiley could not be immediately reached for comment.

As far back as June, Walsh said he would participate in three debates — one with the three other candidates on the ballot during the preliminary contest, and two others with his Nov. 7 rival.

The invitations started coming, including proposals for Walsh-Jackson debates from the Globe and its partners.

The Walsh campaign said that while the mayor “is fully committed to taking part in a debate before the preliminary election,’’ no invitation included all four candidates.

Jackson said he had a tentative date of Sept. 12 for a debate with Walsh, but received an e-mail Tuesday from an organizer with the University of Massachusetts Boston saying the date was scrapped because there was no confirmation from Walsh. The councilor said he is willing to debate Walsh “anytime, anyplace, and with whomever,’’ and that if Walsh believes he has a strong record, he should defend it.

By insisting on a four-candidate debate, the mayor is essentially marginalizing Jackson’s candidacy, said Thomas Whalen, a Boston University political historian.


“Why would you elevate your main opponent as the same level as you are’’ when you can have all four contenders on stage, Whalen said. “It kind of dilutes the political status of Tito Jackson, and I think that is entirely the point.”

In addition, Walsh is attempting to take the political moral high ground, Whalen said, by expressing shock that Wiley and Cappucci are being excluded from debates. At this stage in the game, the other candidates are “background elevator music,’’ Whalen said.

Whalen said Jackson has to be careful about how he responds to Walsh’s demands. Complaining too much would make him look weak to voters, but there is an opening for Jackson, Whalen added.

“He has to play this carefully, express his disappointment,’’ he said. But if there’s a four-man debate, it will put extra pressure on Jackson “to really tighten his punches and focus his arguments’’ against Walsh.

Meghan E. Irons can be reached at meghan.irons@globe.com.