U.S. Rep. Neil Abercrombie's announcement that he will resign from Congress to concentrate on his run for governor is a sign he is going "all in" to energize a campaign that has not gone according to ideal script.

Abercrombie is facing a likely Democratic primary challenge from Honolulu Mayor Mufi Hannemann, who has raised more money than the congressman and has picked up several key endorsements from business and community leaders even though he has yet to formally announce his campaign.

Neal Milner, a University of Hawai'i-Mänoa ombudsman and political analyst, said resigning now is an acknowledgement there is a tough fight ahead.

"The most obvious thing is that he's decided that the campaign is going to be more formidable," Milner said. "It's important for him to press the flesh and be here in person. There are portions of this state that he's never had to run in, like the Neighbor Islands."

Abercrombie's decision throws a curve into the 2010 elections and triggers a special election to fill the remaining months of his two-year term.

Former congressman Ed Case, state Senate President Colleen Hanabusa and Ho-no-lulu City Councilman Charles Djou, who want to replace Abercrombie in Congress, all quickly committed to the special election.

The unexpected vacancy could lead the state Office of Elections to try to come up with as much as $2 million to pay for a special election and scramble to find a voting system because legal challenges have left the state with no voting machines.

"This is an extremely difficult decision for me, but I must do this to continue with the direction I've chosen for the future," Abercrombie said in a statement from Washington, D.C. "Accordingly, I've concluded that I must resign my congressional seat and allow someone to be elected who will carry on the work of this office. The effective date of my resignation will be announced soon."

His term expires on Jan. 3, 2011.

Abercrombie has called a news conference for tomorrow morning at his local campaign headquarters to explain his decision, but told supporters in a statement on his Web site that he wants to focus on change at home.

"Instead of signs of hope and a game plan for recovery, we see a Hawai'i mired in gridlock and confrontation. More time is spent on placing blame than proposing solutions," he said. "In all my years in Hawai'i, I have never seen an election where the stakes are so high. Hawai'i's next governor must be ready to reverse this spectacle on day one and I will devote myself to that task."

Abercrombie's advisers privately used a poker metaphor, saying the congressman was going "all in" on a campaign he has been balancing between Washington and Honolulu since last March. Others described it as a possible "game-changer" after some early setbacks.

TAKING A RISK

Abercrombie, who has served two decades in the U.S. House, initially said he did not plan to leave Congress early.

Free from his congressional duties and the long commute to Washington, he may find it easier to frame issues locally and draw Hannemann out.

But he takes a risk by giving up the aura of being a sitting congressman and the ability to speak out on issues outside the context of his governor's campaign.

Hannemann, Milner said, has a built-in advantage in that he is in local office and can use the power of incumbency to promote himself at press conferences and other appearances.

"Hannemann is really good at combining city work with political campaigning," Milner said.

Several Democrats were struck by the reaction of U.S. Sen. Daniel K. Inouye, the state's top Democrat, who had privately urged Hannemann to run for governor.

Inouye released a statement that wished Abercrombie well but described the announcement as a "surprise and leaves us a vote shy in the House at a time when major policy changes like health care reform, a war spending measure, the Akaka bill and others are shaping up for debate and passage."

Hannemann declined to comment on Abercrombie's announcement. But his spokesman, Bill Brennan, said the mayor agreed with Inouye.

"He agrees with Senator Inouye that, by resigning, Congressman Abercrombie is leaving a puka in the congressional delegation at a time when things like rail, federal stimulus funds, health care and other issues are before the Congress," Brennan said.

Lt. Gov. James "Duke" Aiona, a Republican candidate for governor, said he has no plans to resign his post. "While my opponent has resigned from office, I will honor my commitment to serve my full term," he told followers through Twitter, the social media Web site. "He's been a part of Washington politics a very long time and has grown out of touch with our residents. I'm committed to growing our economy, creating jobs and improving public education."

SUDDEN SCRAMBLE

Abercrombie's resignation also forced the hands of Case and Hanabusa, both Democrats, who will likely have to accelerate their fundraising and grassroots preparations for a special election. The congressman's move also gives new optimism to Djou, a Republican, who may have a better chance in a winner-take-all special election if Democrats split the vote.

Urban Honolulu's 1st Congressional District has favored Democrats but has significant pockets of moderate and conservative voters, particularly on the east side.

Political strategists generally believe the winner of a special election would be the favorite to take the primary and general election to replace Abercrombie.

Under state law, a special election cannot be called any sooner than 60 days from the date of the vacancy.

But with the state Office of Elections struggling with budget cuts and with no voting machines, it is possible the special election will not be held early in the year and could be folded into the September primary.

Hawai'i, under that scenario, could be without full representation in Congress for months.

Case, who won two special elections to replace U.S. Rep. Patsy Mink after she died in 2002 and was posthumously re-elected, said he believes he has the advantage in a special election. "I'm going to step into Neil's shoes on the first day and Hawai'i is not going to miss a beat," he said.

Hanabusa, D-21st (Nänä-kuli, Mäkaha), said she believes she has the skill set as a legislator to serve in Congress. "A legislator is someone who is able to enact laws, get things through, build that consensus, and get the necessary votes," she said. "And that's what you need when you're in Congress. You need someone who is a legislator.

"You also need someone who, obviously, can get along with the rest of the congressional delegation."

Hanabusa said she has no immediate plans to step down from her role as Senate president but will re-evaluate when the date of the special election is announced.

If a special election is called during the next session of the state Legislature, Hanabusa would likely be under pressure to relinquish her post because of the difficulty of running the Senate and campaigning for Congress at the same time.

Djou said he will be distinguished by being the only serious Republican contender and because of his fiscal conservatism. He said he has already heard from the National Republican Congressional Committee about possible financial and tactical help.

"Obviously, this is something that works tremendously to my advantage," Djou said. "If I'm the only Republican candidate, I'm the only clear fiscal conservative in this race."