Congressional seats aren’t vacated often in heavily Democratic Hawaii.

So a scrum ensued within the party when two opened up last year, and is set to culminate Saturday when the Democratic nominees for the open Senate seat and 2nd district House seat are decided. In a year when homegrown President Barack Obama leads the ticket, the winners of the Democratic primaries will be especially favored to win in November.

Sen. Daniel Akaka’s (D) retirement ultimately led to yet another showdown between Rep. Mazie Hirono and former Rep. Ed Case, who previously faced off in the 2002 gubernatorial primary. The Democratic Senatorial Campaign Committee is behind Hirono, whose vast fundraising advantage and internal polling, which has shown her up double digits, indicate she is strongly favored to emerge with the nomination.

Case is hoping a recent autodial poll by the Honolulu Civil Beat, in which he led by 1 point, is closer to reality than the 18-point lead Hirono had in a Honolulu Star-Advertiser poll.

Hirono will face former Gov. Linda Lingle (R), who defeated her in the 2002 gubernatorial general election. But that was a midterm year that was strong for Republicans nationwide, and Lingle will likely need several breaks for this contest to go her way, particularly because this is a federal election.

In the 2nd district, which is being vacated by Hirono, the outcome is less certain in the Democratic primary between former Honolulu Mayor Mufi Hannemann and Honolulu City Councilwoman Tulsi Gabbard.

Hannemann, who was easily defeated in the 2010 gubernatorial primary by current Gov. Neil Abercrombie, began the race with a significant name recognition advantage, but the margin has decreased in the ensuing months, thanks in part to outside help for his opponent. Gabbard, an Iraq War veteran, has benefited from about $600,000 in direct-mail and television and radio ads from VoteVets.org and the independent expenditure arms of the Sierra Club and EMILY’s List.

Hannemann had outspent Gabbard by more than $200,000 as of the July 22 preprimary filing deadline, though Gabbard had a cash-on-hand advantage of $120,000. Hannemann also announced an endorsement from Senate Majority Leader Harry Reid (D-Nev.), a sign the race could be closer than he had hoped.