Hawaii’s door into the U.S. Senate swings open only rarely, which makes the vote in a change election like this one so consequential. The primary contest drew contenders in the two major parties, with Linda Lingle by far the Republicans’ strongest standard-bearer, but it’s the Democratic shootout that has generated all the excitement at this stage.

There, two candidates with substantial records are fighting it out for the top spot: U.S. Rep. Mazie Hirono is vying with former Congressman Ed Case. Both have solid credentials within their party, but Democrats should tap Mazie Hirono as the one best suited to champion Democratic aims and the most clearly distinctive candidate to go up against former Gov. Lingle.

This race evokes a lot of historical parallels. Hirono first faced Lingle a decade ago in their gubernatorial race, in which the Democrat, then the lieutenant governor, was outmatched by the two-term Maui mayor. But that defeat, as well her successful election to Congress four years later, seems to have sharpened Hirono’s game. It’s ironic that Case himself provided the opening enabling Hirono to rehabilitate her resume: In 2006, Case left the U.S. House in a failed attempt to unseat U.S. Sen. Daniel Akaka.

Now that Akaka is retiring, Case is in his second matchup with Hirono — they were Democratic rivals in that 2002 gubernatorial primary. This time he’s challenged by a candidate who has honed her political skills in the intervening 10 years.

Case’s current campaign has reminded politics-watchers of his intelligence and, in several instances, his debating skills, his socially liberal and fiscally moderate stances. He shows a concern about rising costs for Social Security and Medicare that is rational, and a willingness to consider changes for future retirees, such as an increase in the retirement age.

It may come to that. But for Democrats who hew to the party’s core values, including preserving a reliable social safety net, the most prudent choice would be to back a Senate candidate who’s most likely to drive a hard bargain in what certainly will be fierce negotiations over the budget in the years ahead. And that would be Hirono.

Her consistent critique against the Iraq and Afghanistan wars, and a resistance to most military entanglements, should encourage Democrats who also see the need for restraint in international entanglements and controls on defense spending. Hirono says she wishes the Afghan war could be wound down more quickly but accepts the Obama administration timetable, which is informed by ground conditions.

Hirono acknowledges that younger people must not count on Social Security to meet all their retirement needs, but she believes the program must be made more sustainable through the baby-boom surge. She rules out raising the retirement age, which she said would penalize workers with more physically taxing jobs, instead favoring raising the cap on the income levels that are assessed for the Social Security tax, currently set at $110,000. It’s certainly reasonable that it should be set higher than that to fortify the fund.

"If we did that, raising the cap, our trust fund will stay strong for 75 years," Hirono said during an interview with the Star-Advertiser editorial board. "I believe in making the kinds of changes that keep these programs strong without cutting the benefits that our seniors worked for and earned."

Hirono supported the Medicare prescription benefit even though it was not deficit-neutral, with the caveat that the program could be improved fiscally by enabling bulk purchase of drugs. She does not want to see Part D ended.

"I wouldn’t go as the first approach to those options that take away benefits," she added.

She cites with pride her congressional record of bringing home the bacon, rejecting the stigma that has attached to such spending: $2 million to help clean up World War II-era landfill at Bellows, money to repair the Lower Hamakua Ditch irrigation network for farmers. Such items fall far below the radar in Capitol Hill discourse, but she’s right that they are important to constituents. Her three terms in Congress cap a long career of advocacy.

Hirono has long battled the assertion that she is too partisan to move forward a unified agenda, but this time she has begun to answer the charge more aggressively. Alaska Republicans may consider GOP Congressman Don Young a wild card, but Hirono made national news by making a video ad with him about their joint project; at least it blunts the argument that she can’t be bipartisan when it serves Hawaii.

The full primary slates for the Senate seat underscores the interest in this race. John Carroll, Charles Collins, Eddie Pirkowski and John Roco also are contesting on the GOP ballot. Below Case’s name on the Democratic side are Michael Gillespie, Antonio Gimbernat and Arturo Reyes, with nonpartisan Heath Beasley filling out the list.

But there should be no doubt that Mazie Hirono and Linda Lingle have earned the right to make their cases before voters in the general election.