As candidates for San Diego city offices face a Thursday deadline for filing papers to get on the June ballot, one race is distinguished by its last-minute growth in the number of candidates.

Two weeks ago, two people were running in City Council District 1, which includes La Jolla, University City and Carmel Valley — Democrat Barbara Bry and Republican Ray Ellis. Another Democrat, Joe LaCava, dropped out of the race in January.

Then, on Feb. 29, Louis Rodolico, a Democrat and political novice, pulled papers to enter the race. Later in the week, two more candidates joined him — and both are connected to the district’s Democratic incumbent, Council President Sherri Lightner. She cannot seek re-election because of term limits.

The newcomers are Bruce Lightner, a Republican and Sherri Lightner’s husband, and Kyle Heiskala, the councilwoman’s representative to University City and a policy adviser on infrastructure and transportation issues. He has no party preference.

Some have speculated the last-minute growth in candidates was intentional. Elections are decided in June if a candidate wins more than 50 percent of the vote. Rachel Laing, a political communications strategist in San Diego, said the tactic of “ballot crowding” — diluting the votes for each candidate to deprive them of an absolute majority and force a runoff — is a “pretty standard effort” in city politics.

Laing added that having five candidates in District 1 made a runoff more likely and gives Bry a better chance of winning in November. Democrats tend to be at a demographic disadvantage in June elections because their voters are less likely than Republicans to cast ballots then. Democrats to have a higher turnout in November.

Bry and Ellis have downplayed their party affiliations for the nonpartisan office. Bry said she was “very surprised” by the race’s new candidates but that it had not changed her campaign strategy.

“We are still running a grass-roots driven, volunteer effort, talking with voters about their issues,” she said.

Ellis said he was happy to debate issues with serious candidates, but he was concerned the race’s newcomers were playing “political gamesmanship.”

He said Bruce Lightner’s campaign website was a near copy of his own, with virtually identical source code. Ellis added that he is exploring options to legally force Lightner to take the site down.

“That’s very troubling,” Ellis said. “It opens up a whole lot of other questions. Is Mr. Lightner really a serious candidate?”

Bruce Lightner declined to comment for this story. His wife also declined to comment, saying only that she was endorsing her husband as her replacement. Sherri Lightner defeated Ellis in 2012 by nearly 10 percentage points.

Under California law, local elections are officially nonpartisan. But hanging over the entire District 1 race is the chance that it could decide whether Democrats keep their one-vote majority on the nine-member City Council or if Republicans take over.