Rep. Ed Case won't come out and say it, but the underlying message of his campaign to unseat 81-year-old Sen. Daniel Akaka is clear: The old man has to go.

Whether bold or foolhardy, the second-term congressman is abandoning a secure seat in the House to challenge a fellow Democrat who hasn't stirred much controversy with his voting record, created no political scandal and seemed a sure bet for re-election.

The main issue Case, 53, has raised against Hawai'i's junior senator is rooted in the fact that Akaka is 81 years old, just four days younger than Hawai'i's other senator, Daniel K. Inouye.

Case said it was time to "phase in the next generation" when he announced his candidacy.

He shook up the election year with his surprise entry into the race, which likely will be decided in the Sept. 23 open Democratic Party primary. No Republican candidates have stepped forward.

Case is trying to convince voters that Akaka's age puts Hawai'i in danger because the state would lose a lot of seniority in the U.S. Senate if he or Inouye were unable to serve. Case said voters need to plan for Hawai'i's future by electing a younger candidate like him.

"A small state like Hawai'i especially relies upon a continuity of seniority, experience and relationships," Case said in an interview. "What Hawai'i doesn't want and cannot afford is for that continuity ever to be broken."

Akaka turns Case's argument around, saying his age is exactly what makes him the most qualified candidate.

"It's very important to Hawai'i to maintain senior positions there as long as we can," Akaka said in an interview. "When changes are necessary, the people in senior positions can do it and do it well."

Akaka, who has served in the Senate since 1990, is the fourth-oldest member of the Senate, where the average age is 60. The oldest senator is 88-year-old Robert Byrd, D-W.V.

Inouye is No. 3, but he isn't up for re-election until 2010.

When Case announced his candidacy Jan. 19, he got quick rejections from top Democrats like Inouye, Hawai'i-born Sen. Barack Obama, D-Ill., and Hawai'i Rep. Neil Abercrombie. All endorsed Akaka.

But that rallying of party powers around Akaka is exactly what could enable Case to mount a vigorous campaign to convince voters it’s time for a change, said Ira Rohter, a political science professor at the University of Hawai'i.

"He's saying it's time for a new face of the Democratic Party," Rohter said. "He's not just saying, 'Akaka is old and I'm young,' he's saying he represents a new generation."

Case's candidacy likely will force Democrats to consider whether they need younger, more energetic candidates if they're going to keep their majority in Hawai'i's elected offices, Rohter said.

Akaka underwent knee replacement surgery in December 2001 and August 2002, and he had hip replacement surgery in August 2000. He also needed a skin graft in August 2004 to help heal an ankle injury when he was struck with a golf ball.

Philosophically, Case is labeling himself as a moderate who can appeal to independents, while Akaka is more of a traditional Hawai'i liberal.

The liberal Americans for Democratic Action rated Akaka as agreeing with its positions 95 percent of the time in 2005, while Case supported its causes 85 percent of the time. The American Conservative Union said Akaka backed its issues 5 percent of the time in 2004, compared to Case's 20 percent.

Cec Heftel, a Honolulu school board member said Democratic Party operatives derailed his candidacy for governor in 1986.

"I think Case has a very difficult time ahead of him," Heftel said. "It's a shame that there seems to be a suggestion that the loyalty is to the party instead of the people."

Akaka served 14 years in the U.S. House before he was named to replace Sen. Spark Matsunaga, who died of cancer in 1990.

Case was elected to Congress in a special election in 2002 to fill the seat vacated by the death of Rep. Patsy Mink, D-Hawai'i.

Akaka said that if the Democrats took control of the Senate, he and Inouye would be in line for committee chairmanships.

"We are in positions that can take care of and help manage those changes, that transformation, that could help Hawai'i," he said.

Case, a cousin of America Online co-founder Steve Case, said he differs from Akaka in several ways. Unlike Akaka, Case opposes oil drilling in Alaska, and he would have voted for the nominations of Secretary of State Condoleeza Rice and Supreme Court Chief Justice John Roberts. He said he also has differences with Akaka on the budget, reform of the litigation system and foreign policy.

"It's not that there's something innately wrong ... it's about the fact that we have to move on," Case said. "It's not a comment on Sen. Akaka, it's a comment on the way things are."