Finally, a race both interesting and important.

As former Gov. Ben Cayetano edges toward his expected declaration, the Honolulu mayor’s race is shaping up to be the locus of political interest.

If explicatives are all you hear from the boys in the back room, it is because Cayetano, the up-by-his-bootstraps Democrat, is fixing to throw the entire cozy political scene out of focus.

The overriding truism of Hawaii politics is that when Democrats are aligned with the unions, the Democrats win.

Former Gov. John A. Burns did many great things as he formed Hawaii modern Democratic Party, but central to his success was his ability to forge a relationship with the ILWU, then the most powerful union along the docks and across the plantations. ILWU leaders became Burns’ appointees and a government relationship was formed. Later the Hawaii Government Employees Association and the United Public Workers union would overtake the ILWU in political influence, but still unions were powerful only if they held hands with the state and city government bosses.

Enter Democrat Cayetano, about to jump into the nominally nonpartisan race for mayor. If and when he goes, he will not have support from the Democratic Party, but what about the unions?

The building trade unions are solidly behind the $5.3 billion city rail project. Construction is still hurting, the trade unions are all on the bench and they will support either current Mayor Peter Carlisle or former acting Mayor Kirk Caldwell, who want to build the train project.

Public worker unions have a slightly different equation to solve. They work for a city or state government that continually doesn’t have enough money. The state has a marginally balanced budget today, but two years from now it is projected to be hundreds of millions of dollars out of balance.

Every year Honolulu’s train sucks about $350 million out of Honolulu taxpayers in increased general excise tax collections. Do teachers and white collar government workers and firefighters want to keep on worrying about ever getting a pay raise or do they want to get that extra $350 million a year?

Added to the public unions’ fears are the completely unbalanced state payments to the state retirement system and the state worker medical insurance plan. Can the state continue to afford to pay the health insurance benefits for retired public employees?

So Cayetano, who left office as something less than the HGEA poster boy, can make an argument that putting the brakes on the train means there could be more money for public workers.

In his campaigns for governor, Cayetano drew support across the middle of Oahu, winning historically Democratic areas from Punchbowl through Kalihi and across Pearl City into Ewa. Those are many of the areas that Caldwell won in his loss to Carlisle two years ago. So you could argue that Cayetano would take votes away from Caldwell in Democratic areas.

Cayetano did not do well along Oahu’s Windward side and in valleys of East Hono- lulu stretching out to Hawaii Kai. But Carlisle did do well there, because he walks and talks like a Republican, even though he says he isn’t.

Veteran Republican Sen. Sam Slom, who has joined Cayetano in a lawsuit to stop rail, swears that Cayetano the Democrat can win GOP voters because they just hate rail.

"I was at an 8th Senatorial District meeting two weeks ago and I told the crowd I supported him and they all cheered," Slom reports.

I reminded Slom that Cayetano is a Democrat and is going to remain a Demo- crat. There will not be GOP patronage coming out of a Mayor Cayetano administration.

"The primary reason Republicans want Cayetano is that they recognize that this project will destroy everything we have," Slom says.

Of course, the other side is that without this project, Carlisle and Caldwell argue, Oahu is doomed to traffic hell. Cayetano counters that there are less economically destructive ways.

This year, the race for mayor of Honolulu will go a long way to redefining Hawaii’s political structure.

Richard Borreca writes on politics on Sundays, Tuesdays and Fridays. Reach him at rborreca@staradvertiser.com.