The ballot has been winnowed, the races set for November.

In a low-turnout preliminary election, Boston voters on Tuesday narrowed a lengthy list of candidates running for City Council, teeing up what could be a historically diverse Boston legislative body.

All four of the city's incumbent at-large councilors — Michelle Wu, Annissa Essaibi-George, Michael Flaherty and Althea Garrison — will be on the final ballot. They'll be joined by four challengers: Alejandra St. Guillen, Julia Mejia, Erin Murphy and David Halbert. The top four vote-getters will make the council.

On Tuesday, Wu — whose name has been floated as a possible mayoral challenger — was the top vote-getter among the at-large candidates, according to the unofficial results. Garrison, a conservative who moved onto the council after Ayanna Pressley won a congressional seat, finished behind St. Guillen and Mejia.

Both St. Guillen and Mejia are trying to become the first Latinas on the council.

Three white male incumbents opted not to seek re-election, leaving open seats in Districts 5, 8 and 9.

In District 5, which includes Hyde Park, Roslindale and Mattapan, Ricardo Arroyo — the son and brother of former councilors — topped voting, and will face off Nov. 5 against Maria Esdale Farrell.

In District 8 — which runs from the West End, through Back Bay, and to Mission Hill — Boston Housing Authority official Kenzie Bok got 50% of the vote, and will go against Jennifer Nassour, a former state Republican Party chairwoman, who finished with 18%, per the unofficial tally.

And in District 9, covering Allston and Brighton, Craig Cashman and Liz Breadon will square off in November.

In Roxbury, District 7 incumbent Kim Janey also had two challengers. Janey got 70% of the vote Tuesday, and will face Roy Owens Sr. on the final ballot.

The preliminary election — conducted on the same day U.S. House Democrats decided to move forward with an impeachment inquiry into the president — drew light turnout. Just about 11% of the city's voters cast ballots, Boston officials said.