According to current state law, the special election for the vacant Senate seat will be held in 145-160 days, which would mean either January 19, January 26, or February 2.
The party primaries for that election must be held six weeks earlier, which would be either December 8, 15, or 22.
I am getting informed speculation, however, that there may be a proposal to change the law -- aside from any change concerning a temporary appointment. The change would reduce the 145-160 days to something like 105-120 days.
This would allow the state to schedule the primary on November 3rd, the same day as the municipal elections that will be held all over the Commonwealth, including Boston. The general election for Senate would then fall six weeks later, on December 15.
The arguments for the change are as follows:
--The state and municipalities would save a truckload of money by combining the municipal and primary elections.
--The duration of Massachusetts lacking full representation (or represented by a temporary appointee) would be reduced by over a month.
--The newly elected Senator would be chosen and sworn in before the Senate resumes work after the New Year.
--The special election campaign would be over before the holidays, whereas under the current timetable the general-election campaign would take place over the XMas-New Year season, when people are not around or paying attention.
Obviously there can be much debating about which potential Senate candidates would benefit from this change. But it would definitely have an effect on the municipal elections, which presumably would see much, much higher turnout on November 3rd if the US Senate primary was also on the ballot that day.