Less than a third of the people who vote could choose Philly’s next mayor. Is that normal?

Mayor Jim Kenney’s winning number was 130,775. Michael Nutter’s was 106,805. In this year’s crowded, highly competitive mayoral field, the number of votes that advance the candidate likely to be the next mayor of the city could be much, much lower.

It’s not just that there’s a lot of people running — Philadelphia is used to crowded ballots. It’s that the Democratic race has remained tight up until the end.

Usually, one or two candidates pull away. With three or four running even, as recent polls suggested, some speculate Philadelphia’s next likely mayor could be decided by the smallest share of the vote in modern mayoral history.

“I would bet a slice of pizza that no one breaks 30 [percent],” said political strategist Neil Oxman, who has worked on every open Philly mayor’s race since 1979 but sat out this one.

Polls don’t always predict the outcome on election day, of course, and with 15% of likely voters undecided, it’s still possible one candidate winds up winning by a larger margin.

Philadelphia is home to more than 1.5 million people, 775,000 of whom are registered Democrats eligible to vote in the party’s mayoral primary on Tuesday. The vast majority won’t vote (only 30% did in the last competitive mayoral in 2015), and those who do are often whiter, wealthier, and older than the rest of the population.

In seven of the last 10 competitive primary races, at least five candidates have been on the ballot. However, in every mayoral contest since 1971, every victor won at least one-third of the primary vote. Those winning totals generally represent just a fraction of the overall registered voting-age population, as turnout has slumped year after year.

This includes even 1979, the most crowded Democratic primary seen over the past half century. That year, 11 candidates duked it out for the privilege of succeeding controversial Mayor Frank Rizzo, the former police commissioner who had unsuccessfully sought to modify the city charter to stand for a third term in office.

Still, the vast majority coalesced around two well-known Democrats — attorney and civil rights leader Charles Bowser, and future Mayor Bill Green III.

In 2007, longtime Councilmember Michael Nutter won a seven-way primary — including four other political heavy hitters — with just 106,805 votes. That represented just 36.6% of the total votes cast in the primary. In 1999, John Street similarly bested five opponents with a total of 107,285 votes.

This year, some political strategists and operatives working on the campaigns predict the total number of votes the nominee gets could fall far below 100,000. That would be the lowest winning raw vote total since at least the 1970s and would represent less than 10% of all registered voters, according to an Inquirer analysis of past election data.

Mustafa Rashed, a political consultant uninvolved in any of the campaigns, guessed the winning percentage could be as low as 25% of the vote. That would be in the range of 65,000 to 80,000 votes, assuming turnout is in the mid-to-high 200,000s or low 300,000s.

“The nominee will have to immediately demonstrate how they intend to be the mayor for the entire city and not just one small fraction of the voting electorate,” he said.

The share of total registered voters the next Democratic nominee will win — a figure that has long hovered around 1 million in Philadelphia — tends to be slim, and has generally declined over time.

Pennsylvania features a closed primary system, where only registered members of a political party may participate in that party’s primaries. That naturally limits how many voters can influence the Democratic primary, which has long determined who goes on to win the general election in a heavily blue city like Philadelphia.

Out of these 10 past competitive Democratic mayoral primaries, an average of just 18% of all registered voters cast ballots for the winning candidate. Nutter’s primary win represented just over 10% of all registered voters.

But, over time, voter turnout has notably declined in Philadelphia, much like other big-city Democratic strongholds.

Among competitive contests, the three highest-turnout Democratic mayoral primaries over the past half century all occurred between 1979 and 1987. The three lowest turnout races all occurred after the year 2000.

Primary participation peaked around 70% in 1983, with 625,201 votes cast out of 899,882 registered Democrats. That heated contest notably ushered in Philadelphia’s first Black mayor, Wilson Goode Sr., who faced off against Rizzo as the former mayor sought to return to office for a third, nonconsecutive term.

“What makes people vote is either you really love someone or you really hate someone,” Oxman said. “Rizzo was the bogeyman, and Wilson Goode was portrayed as a giant so you had a gigantic turnout.”

He called this year’s race “fairly uninspiring.” While, the candidates have appealed to different voting blocs, there’s some overlap and overall, passions aren’t running quite as high as they were in ‘83. “No one hates anybody,” Oxman said of voters’ attitudes toward the field this year.

Overall Democratic voter registration decreased 13% between Goode’s election and the 2015 Democratic primary — the city’s last seriously contested mayoral race.

But that year saw particularly dismal turnout, with just 30% of 776,690 registered Democrats casting ballots in the contest that nominated outgoing Mayor Jim Kenney.

This year’s tightly contested race has prompted some discussion — largely among highly informed voters — about the benefits of ranked-choice voting. Proponents of the voting system say it elects candidates with more consensus support than a traditional winner-take-all election. The system also has its critics, who say it can be complicated for voters and costly. It would require buy-in from both City Council and the state legislature to be implemented.

For now, candidates are making a final push in an attempt to turn out enough of their base and win over undecided voters.

A tight finale is nothing new.

Reporting from the 1991 mayoral primary, which then-district attorney Ed Rendell ultimately won, found voters who said they had grown less certain about who to vote for over months of campaigning by four Democrats running on similar platforms.

“I’m so undecided,” Naomi Lingham, a 73-year-old from North Philadelphia, told a New York Times reporter that year. “It’s a sin.”

Staff writer Leo Cassel-Siskind contributed to this article.