With eight months to go until Hawaii’s 2016 primary election, several high-profile names have emerged as potential challengers to Honolulu Mayor Kirk Caldwell’s re-election bid.

No one has formally declared their candidacies and nomination papers won’t even be available until Feb. 1. But several high-profile political figures have suggested that they are looking seriously at the race.

Former Hawaii Lt. Gov. James “Duke” Aiona is raising the most eyebrows after stating last week that he will “neither confirm or deny” interest in the executive suite at Honolulu Hale. But he acknowledged that he has been approached by people to run, and did not hesitate to criticize Caldwell or his handling of the city’s now $6.58 billion rail transit project.

Former Mayor Peter Carlisle, who was ousted after he finished third in the 2012 runoff round to Caldwell and former Gov. Ben Cayetano, said he is weighing whether to wage a campaign to regain the mayor’s seat. He said he is not interested in running for city prosecutor, his other former high-profile job.

And then there’s City Council Chairman Ernie Martin, who has said for a while that he intends to run for mayor at some point in his career. Like Aiona, Martin has openly criticized Caldwell and his handling of rail and his policies on dealing with the homeless.

Not running is Vicky Cayetano, the former governor’s wife. She acknowledged that she has also seriously considered a run after being approached by potential supporters, but said she has chosen not to run, at least not in 2016. Her husband, Ben Cayetano, said he also does not intend to run for mayor in 2016.

Aiona told the Honolulu Star-Advertiser last week that he will “neither confirm nor deny” that he is considering a run for mayor. A Republican who would be running in a nonpartisan race, Aiona said people have urged him to run for mayor “and for other races, also.”

In response to questions about Caldwell’s performance, Aiona said, “I think this mayor has not done a good job … I think he’s doing a terrible job in regard to many of the issues confronting the people of this county.”

Aiona said he disputes Caldwell’s claim that he’s done well at fixing potholes, pointing out that his vehicle has been running over the same cracks for seven to eight years.

“I firmly believe he is the consummate politician,” he said. “He will bend whichever way the wind is blowing.”

On the rail project, Aiona reiterated that he has always been opposed philosophically to rail because of its high cost. As a candidate for governor, Aiona said, he told voters he would not oppose rail “because it already had started and because it was a city project.”

Now its rising cost “is a major concern,” he said. City officials “can’t put their hands around it, and there’s always something that’s coming up on it.”

He also suggested that he would have opposed extension of the 0.5 percent general excise tax surcharge — which Caldwell has lobbied heavily for — that was passed by this year’s Legislature and is currently being debated by the City Council.

Asked if he thinks whoever is mayor would be able to stop the project now, Aiona said he’s not in a position to say since he’s not been privy to the information received by Caldwell and Council members.

“Stopping rail right now and tearing it down is an option,” Aiona said. “Now is that the most economical option out there? Is that the best option for the residents of the county of Oahu? I don’t know.”

After losing the 2014, three-way gubernatorial election as the Republican nominee against Democratic winner David Ige and independent Mufi Hannemann, Aiona spent some time as executive vice president at Saint Louis School, his alma mater. In January, he was appointed executive director of the conservative Hawaii Family Advocates.

Carlisle said he is considering his options for 2016 “and running for mayor is one of them.”

He said his wife “isn’t particularly enthusiastic” about his re-entering politics, noting that he draws a larger paycheck and is able to spend more time with his family as an attorney in private practice with the firm O’Connor Playdon and Guben.

However, Carlisle said, “I’m not particularly impressed by what’s going on at City Hall right now … there’s a void in leadership.”

Furthermore, “frankly I miss being a part of running the city. It’s a lot of fun and you get to get a lot of things done,” he said. “In all honesty, I’m tired of politics as usual, I’m tired of partisan stuff, I’m tired of people making promises and breaking them, and I’m tired of money being spent foolishly and unwisely.”

Carlisle said he still is an ardent supporter of rail, although “I’m concerned about whether all of the costs are legitimate.” However, he said, the mayor is no longer responsible for the project because it is in the hands of the Honolulu Authority for Rapid Transportation.

Many expect Martin, who’s led the Council since the summer of 2011, to challenge Caldwell although he has not said what he will do in 2016. First elected in 2010 to represent the district that runs from Mililani Mauka to Kahaluu, Martin won a second, four-year term in 2014 and will not be eligible for another consecutive Council term when his current term ends in 2018.

Martin reiterated on Wednesday that he continues to aspire to be mayor. But despite a number of high-profile disagreements with the current mayor on rail, homelessness and other issues, Martin said he has not made up his mind about whether to challenge Caldwell in 2016.

“That’s something for me, I’ve always felt would be the next logical step in my career,” Martin said about his ambitions to be mayor.

“For me, right now, all of my efforts are focused on the issue of rail and the GE tax surcharge,” Martin said. “Until that issue is settled and put to bed, it wouldn’t be fair to those who elected me to focus on anything else.”

The Council Budget Committee is taking up the matter again in the coming weeks and a final vote of the full Council is expected at the end of January on the controversial decision on whether to extend the tax surcharge by five years through 2027.

Martin, who has always supported rail, has been critical of HART’s management and proposed a cap be placed on how much of the surcharge extension would be allowed to go to the project.

The Hawaii Constitution would require Martin to resign from the Council before running for a different state or county office in 2016. The deadline for candidates to file for a 2016 seat is June 7 and Martin likely would not want to declare a candidacy until just shortly before then.

Martin acknowledged that he and Aiona had breakfast the day after news broke that the former lieutenant governor maybe interested in challenging Caldwell, and that they talked politics. Martin described Aiona as “a supporter and a mentor.”

Like him, Martin said, Aiona “lacks a level of confidence” with Caldwell’s leadership. “Somebody needs to step up and …. provide an alternative choice (to Caldwell).”

The Star-Advertiser spoke separately with former Gov. Ben Cayetano and his wife, self-made businesswoman Vicky Cayetano.

Ben Cayetano said he might be making a run “if I was five years younger,” and cited some noncritical health issues as factoring into his decision.

Vicky Cayetano said she was approached by people to run and seriously considered doing so and, like others, cited what she felt is a lack in strong leadership.

“Honolulu residents deserve to live in a city which is managed in a fiscally responsible manner,” Vicky Cayetano said. “Honolulu should be a city that balances growth and development with environmental and infrastructure needs.”

Caldwell was on a family vacation and out of town. Lex Smith, his campaign spokesman, said he believes the re-election team can confidently stand on the mayor’s record of accomplishments and rebut any negative points that challengers may make.

“We think the mayor has done a darn good job and we are confident in defending his record,” Smith said. The Caldwell administration has had to deal with tough challenges on issues including rail and homelessness “and not backed away from them,” he said. “And it has taken appropriate measures to deal with them.”

Local political observer Colin Moore, a University of Hawaii at Manoa political science professor, said he thinks Caldwell has to be considered the clear-cut favorite to win re-election at this juncture.

“My impression is that the mayor is in a good position,” Moore said. “If you think about about the fundamentals, I think he’s relatively well-liked … he has a bunch of money (in his campaign treasury) … he’s fixed the roads and that seems to be a big plus with the voters.”

But there are legitimate reasons for Caldwell to look behind his back, Moore said. “He is vulnerable on a couple of issues, which are rail and homelessness.”

Because Aiona is the only one of the three potential Caldwell challengers who publicly opposed rail, he may be in the best position to capitalize on the growing disenchantment with the most expensive capital improvement project in Hawaii history.

“He has a history of being opposed to rail, he will have access to Republican donors (in a nonpartisan election) and he’ll be able to turn out his socially conservative supporters. I can see that campaign taking shape,” Moore said. “If I were Caldwell, he’s the one that I’d be worried about.”

Carlisle and Martin, while they have tried to carve somewhat different stances on rail than Caldwell, nevertheless still support the project “so there aren’t any real big policy differences” for them to distinguish themselves from the incumbent.

Moore said, however, he’s not sure those with strong feelings against rail can form a core that can defeat Caldwell. “The truth is I think Caldwell is going to be tremendously hard to beat.”

City elections are held in a nonpartisan run-off style. The first “special election” is on Aug. 13, concurrent with the state primary election. The two top vote-getters in city races then face off in the second special election on Nov. 8, general election day. The exception to that rule is that if the No. 1 finisher in the first election captures more than 50 percent of votes cast, that candidate wins outright and no second election is held.

In 2012, Cayetano was the top vote-getter in the first election with Caldwell finishing second. Carlisle, who finished third, was eliminated. In the second election, Caldwell beat Cayetano.