Despite repeated setbacks and one outright rejection, the A’s aren’t giving up on any of the three potential stadium sites they’ve been working on in Oakland.

That’s the word from team President Dave Kaval, who tells us he’s still aiming for the A’s to have a deal for a new ballpark — somewhere — by year’s end.

“That’s kind of our deadline,” Kaval said when we reached him at the A’s spring training camp in Arizona.

The A’s don’t have a lot of reasons for optimism lately. The latest bad news was BART General Manager Grace Crunican’s letter to the team that nixed the idea of building a station near a possible stadium site on the Oakland waterfront because it would be costly and too disruptive to transit service.

“I don’t think one letter rules out a BART station,” Kaval said — though he acknowledged that a station at the Howard Terminal site might not happen until well after a ballpark is built.

In the meantime, he said, Crunican’s letter provides “a great opportunity for the stakeholders — BART, the city, the port and us — to get together to find a creative solution at Howard Terminal,” such as “a robust transportation plan” that could include a rapid-bus tram to the 12th Street and West Oakland BART stations.

BART’s “no go” follows the “no go” by the Peralta Community College District Board of Trustees, which rejected the idea of even talking with the A’s about their preferred ballpark site next to Laney College.

Kaval said the third option of rebuilding at the Coliseum is now “probably the front-runner” in terms of getting a ballpark built quickly. But he said its location — five miles from downtown — is still a problem.

“We have seen across baseball that the most successful urban ballparks are downtown,” he said.

Kaval said the team has met with groups interested in partnering with the A’s to develop the Coliseum site. But he said anything built there would have to “be complementary to a ballpark ... and that’s the part that hasn’t been solved yet.”

The good news for fans is that the A’s are not threatening to move elsewhere. Kaval is sticking to the team’s mantra that “we are committed to Oakland and a site that works.”

Shock talk: London Breed’s newfound support for arming cops with Tasers hasn’t won the mayoral candidate any points with the San Francisco Police Officers Association.

Breed has been a vocal supporter for police reforms, but only recently came out publicly in support of Tasers.

“I’m not surprised at the change — I think that she is just being advised by her consultants to come more to the center,” said police union President Martin Halloran.

Breed said her support for giving the electronic stun guns to police as a less-lethal alternative to firearms has a simple explanation: “I hate guns. Guns have destroyed the lives of so many in my community.”

The Board of Supervisors president noted that the Obama administration’s Justice Department urged the city to “strongly consider” arming cops with Tasers in a 2016 report that recommended several police changes in the aftermath of a rash of officer-involved shootings.

The Police Officers Association was an early supporter of Breed’s first supervisorial campaign, in 2012, as well as her re-election effort four years later. However, the union later rescinded its re-election endorsement when Breed joined critics of the department in the aftermath of the December 2015 police shooting of Mario Woods.

The union has yet to make an endorsement in the June mayoral election. “And I don’t see us making one in the near future,” Halloran said.

Voters will have their say on the Taser issue in June, on a police union-backed measure to arm officers with the stun guns. Polls have shown support for the idea, and Breed’s switch could be a way for her “to help define herself with voters on the city’s more moderate west side,” said political consultant Tom Hsieh Jr., who is not working with any mayoral campaign.

Mayoral candidate Angela Alioto, who has long supported Tasers for police, expressed mock surprise at Breed’s stance.

“Oh, she came out for it? Will wonders never cease,” the former supervisor said.

The other two leading mayoral hopefuls, Supervisor Jane Kim and former state Sen. Mark Leno, remain opposed to Tasers.

“There’s a lot of flip-flopping that happens during campaign season, but I’ve been consistent,” Kim said. “We need to provide our police officers with the training and resources they need to de-escalate situations safely.”

As for Leno: “No one is talking to me about Tasers,” he said. “It’s a distraction.”

S an Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or email matierandross@ sfchronicle.com. Twitter: @matierandross