In Hawai'i politics, it has long been felt that the best way to predict an election — barring any other overwhelming factor — is this:

"As the unions go, so goes the election."

That's been a reasonably dependable rule of thumb over time, at least since the unions cemented their organizational muscle in the years following World War II and statehood.

But as strong as they are, politically, the unions are not invincible. They've had their share of defeats, including last Tuesday at the Democratic precinct caucuses.

Union strength, at least the American Federation of State, County and Municipal Employees union, was officially behind nominee Hillary Clinton, who also enjoyed backing from other power brokers such as senior U.S. Sen. Daniel K. Inouye, D-Hawai'i.

But all their institutional strength and organizational savvy were helpless against Obamamania, the incredible popular surge of support and excitement about home-grown candidate Barack Obama.

Does that mean the days of union domination of politics, particularly Democratic Party politics, are over?

Hardly.

The Obama phenomenon was a once-in-a-lifetime thing, most likely. In a year or two, politics will likely sink back to the point where organization and well-honed political skills will once again count for plenty. And that is where the unions come in.

This hiccup, however, marks a good time to step back and think about how the unions gained so much power in Hawai'i and what made them tick.

To do so, you could do no better than to tune in tomorrow at 8:30 p.m. on KHET/PBS Hawaii to catch a most intriguing biographical film on one of Hawai'i's most famous labor leaders: Jack Hall.

"Jack Hall: His Life & Times," is a new biography produced by the Center for Labor Education and Research as part of the long-running Rice and Roses series.

By chance, it will show just as "A Spark Is Struck: Jack Hall and the ILWU in Hawaii," the seminal biography of the labor leader by the late Sandy Zalburg, has been reissued by Watermark Publishing.

A lot of people new to the Islands or new to politics and unionism might not know the full story of the rangy, brainy, hard-drinking Mainland haole who built the Island International Longshore and Warehouse Union into the powerhouse it remains today.

This documentary, which pulls together archival photos (and rare film footage), actors using the actual words of Hall and others along with contemporary interviews, is a sparkling and inspiring look at a key piece of Hawai'i's contemporary history.

It touches on dark times, such as being hauled into court on charges of communism during the McCarthy era. But it is largely a tale of how the collective voice of little-noticed agricultural and dock workers became a power that changed the lives of its members and the society around them.

In the words of Ah Quon McElrath, the longtime social activist and union leader, Hall's efforts led to the "awakening of the human spirit by a group called a union."

It is nearly impossible to overstate the impact Hall and his associates at the ILWU had on the economic and political structure of the Islands. The union and its people forevermore had a "seat at the table."

McElrath remembers Hall's last poignant visit to the Islands in 1970, when the veteran labor leader (then living and working in San Francisco) was weakened by the effects of Parkinson's and years of hard living.

It was clear, she said, that Hall wanted one last look at a place his beloved union had transformed so fundamentally through years of struggle and organizing.

Today, with the decline of agriculture and the growing middle-class comfort of its members, the union may have declined in size, strength and militancy.

But it would be a mistake to write off the ILWU and the union movement as yesterday's political news in Hawai'i, no matter what happened on Tuesday during those caucuses.

Jerry Burris' column appears Wednesdays in this space. See his blog at blogs.honoluluadvertiser.com/akamaipolitics. Reach him at jrryburris@yahoo.com.