Former Gov. Ben Cayetano entered the 2012 race for mayor Thursday, vowing to kill the city’s $5.27 billion rail transit project while acknowledging his anti-rail campaign might go against the political idealogy of some longtime supporters.

"I’ve been through eight elections, and this is the first time I’m going to be on the other side of many friends and former supporters," Cayetano said at a news conference announcing his campaign.

Cayetano’s entry creates a three-way contest with incumbent Mayor Peter Carlisle and former city Managing Director Kirk Caldwell, all experienced candidates and each appealing to similar constituencies.

"Cayetano is a very formidable candidate who really has a good shot at winning," said Neal Milner, University of Hawaii political science professor emeritus. "The main reason is because he isn’t just a one-issue candidate. He’s not simply an anti-rail candidate. He’s an experienced politician and a tremendously successful vote-getter."

Carlisle was in Washington, D.C., attending the U.S. Conference of Mayors winter meetings.

Cha Thompson, his campaign manager, issued a written statement challenging assertions that the rail project will bankrupt the city and highlighting Carlisle’s efforts to trim city spending.

"It’s an investment in the next generation, offering commuters a quality of life choice in dealing with traffic misery," Thompson said. "Mayor Peter Carlisle is committed to bringing fiscal discipline to the city. He will grow our economy by continued investments in sewer upgrades, road repairs and other infrastructure projects."

Caldwell questioned whether Cayetano’s credentials would translate in city government.

"Ben has never served on the City Council and never, never has worked in city government," Caldwell said. "He doesn’t understand the issues of the city, and they are very, very different. I know that. I served in the state Legislature. … It’s up close, personal and immediate. I don’t think Ben understands that."

Cayetano, the former two-term Democratic governor, has served 28 years in elective positions. He left office in 2002 after his second term as governor.

Carlisle, the former city prosecutor, has served nearly two years as mayor after winning a special election in 2010 to fill the final two years of the term vacated by Mufi Hannemann, who resigned to run for governor.

Caldwell is an attorney in private practice who also served in the state House from 2002 to 2008 before moving on to become managing director under Hannemann in 2009.

"Being mayor means being hands on," he said in a statement after Cayetano’s announcement. "And let’s get something straight right up front, rail transit is an important issue in this election. However, this election is about so much more. It’s about the buses that take people to and from their jobs every day, the HandiVan service, bus passes, it’s about protecting people and their property, filling pot holes and repaving their roads."

The race could force voters to decide between political philosophy and their stance on the rail project.

Both Carlisle and Caldwell are strong supporters of rail, which appeals to construction-related unions that see the project as creating jobs.

Although the race is nonpartisan, many voters might still side with their party, meaning longtime Democrats Cayetano and Caldwell would be vying for the same voters.

A candidate can win outright in the Aug. 11 primary by capturing 50 percent plus one vote. If not, the top two would advance to the November general election.

"I would say that Carlisle and Cayetano have certain advantages that Caldwell doesn’t have," Milner said. "But Caldwell might be able to pull it off as the survivor if the other two beat each other to death."

Cayetano brings name recognition to the race but would have to convince voters he can deal with the day-to-day task of running the city.

Cayetano said he would release details next week of his plans for the city’s sewage and secondary treatment plant upgrades, road repairs and other city projects.

Much of that would be tied to a less expensive mass transit alternative.

Cayetano said he supports the concept of an express bus or trolley system using dedicated freeway lanes, citing former Mayor Jeremy Harris’ Bus Rapid Transit system proposal as an example of a less costly project that could achieve similar results as rail. Investing only $1 billion on a transit system would free funds that could then be put toward upgrading sewers, although doing so would require legislative support.

"I would tell them (state lawmakers) I don’t need this much money for transportation, but let me use the rest of it to help fix the sewers and the water system," he said.

Cayetano also pitched his friendship with Gov. Neil Abercrombie, dating to their time in the Legislature, as an asset that would benefit the city. Political tension would be absent because, Cayetano said, he would not be interested in Abercrombie’s job.

"I’ve been there. I’ve done that," he said. "I’m running for mayor. Period."

Cayetano had supported Carlisle’s campaign in the 2010 mayoral race, but Cayetano changed his support as his stance against rail grew stronger.

Caldwell said he thought he had Cayetano’s support after a breakfast meeting several months ago in which he sought the former governor’s backing. He said they agreed to disagree on rail and that he was surprised when he learned of the former governor’s candidacy.

Cayetano said he asked Caldwell to consider the arguments against rail, and if he still decided to go with it, to make sure it was done right, and left it at that.

"He had to choose between taking that kind of approach and irritating the labor unions," Cayetano said. "When I figured out where he was going, then I decided that I wasn’t going to support him."

Hawaii News Now video: Ben Cayetano announces Honolulu mayoral bid