ADAM KLINE, the state senator from Central and Southeast Seattle, is clearly pissed off, though he pretends not to be. The reason: fellow Democrat Dawn Mason’s decision to give up her House seat and take him on in the September primary, making a safe Democratic seat one of the most bitterly contested races this election season. In the overwhelmingly Democratic 37th District, whoever wins the primary wins the seat.

“She’s got a right to run,” Kline allows as we talk in his Pioneer Square law office. An hour later, his tone has changed: “I think she owes the voters an explanation. She’s drawing Democrat donors’ money and volunteer time when it could be directed at other districts to beat Republicans.”

Much of the Democratic establishment appears to feel the same way; Kline’s endorsement list includes Gov. Gary Locke, King County Executive Ron Sims, and the 37th District Democratic organization. Defenders of party protocol point out that Mason was all but handed the seat on a silver platter two years ago when Democratic officials sought a replacement for its previous occupant, Dwight Pelz, who left midterm to take the County Council seat Sims had vacated. “Everybody knows she could have had the seat if she wanted it,” says Pelz.

At that time, she didn’t. She says it was a matter of keeping faith with her constituents. “I had just ran a race where I had to convince voters that I really should go back to the House,” says Mason, a part-time management systems analyst for Seattle Public Utilities, speaking in the campaign office at her Hillman City home. Never mind that at the same time she applied to fill a Seattle City Council vacancy, a more elite and better-paying job (which she didn’t get). Mason wants the Senate seat now.

Mason doesn’t just shrug off party protocol, she positions herself in opposition to it. “I’m not an insider,” she explains in her customary amused and confiding tone. “I’m a pretty grassroots, pretty populist sort of person.” As a black woman, she’s to some extent cast in that role in a way that Kline, a white man, isn’t. But like former mayoral candidate Charlie Chong, Mason accents her outsider status by tweaking supposed stuffed shirts. Kline, she says, takes her challenge “too personally.”

Other outsiders—Chong, for one—gravitate to Mason ‘s campaign. Her supporters also include the Rev. Samuel McKinney, a pillar of the local black community, Rep. Frank Chopp and other legislators she has worked with, and City Council members. Tina Podlowdowski expresses what others surely feel when she says, “I think it’s really important to have African-American voices in the state Legislature.” Mason has been one of only two black legislators.

Mason herself makes the point more forcefully. “Do I think there would be a horrible loss to the state of Washington if I were no longer a legislator? Yes, there would be.”

SOME OF MASON’S SUPPORTERS go as far as to suggest that the candidates’ constituencies differ along racial and economic lines, with Kline getting the largely white and affluent lakefront neighborhoods, and Mason, the Central Area and Rainier Valley, which, despite gentrified pockets, remain largely black and Asian, and hold many of the city’s poorest residents.

But Kline, a classic liberal, has made it his business to consider minority needs. Last year he sponsored a bill to broaden the reach of low-interest state loans to women- and minority-owned businesses by funneling them through nonprofits as well as banks. (Nonprofits tend to lend to smaller businesses.) The bill ultimately failed.

Al Sugiyama, executive director of the Center for Career Alternatives, recalls how Kline visited his office and other organizations serving minorities. “I like the fact that he came down here and really tried to be helpful,” he says. Though he says he was one of the first Asians to support Mason in previous races, Sugiyama endorses Kline in this one. Kline’s race is no drawback, Sugiyama notes: It “gives good balance” to a district that is one-third white, one-third black, and one-third Asian. The 37th’s legislative delegation has traditionally represented that balance: Rep. Kip Tokuda rounds out a team that until now included Mason and Kline. Earlier, Pelz (white), Locke (Asian), and Jesse Wineberry (black) reflected the same balance.

Racial differences are bound to be noticed, however, when candidates sound nearly identical on the issues. Both Kline and Mason pronounce support for more funding for schools and economic development in the district. One rare point of difference is charter schools, a perennial legislative flashpoint. Mason (who first came to prominence in a mid-’80s effort to overturn Seattle Schools’ mandatory busing) is for them; she says they foster parental choice. Kline believes they siphon resources from the public schools that serve most kids.

DESPITE THEIR ideological similarities, the two didn’t get along well last year in the Legislature. Kline blames Mason, one of the Legislature’s few minority members, for killing his minority-lending bill by letting on that she opposed it. Mason explains that she thought the bill would take money away from those who now get it, rather than opening up new funds for smaller businesses.

Mason also withheld support from a Kline bill that did pass, instituting automatic driver’s-license suspensions in drunk-driving arrests (as in most other states). Before, suspensions required a court hearing. Under Kline’s legislation, defendants may seek to regain their licenses in administrative hearings.

Mason derides Kline’s bill as “Republican,” arguing that it denies defendants due process in court. It’s true that many House Democrats did vote against it—led by then­Minority Leader Marlin Appelwick (now an appeals court judge), who feared it would undermine a program that lets first offenders stay licensed if they undergo alcoholism treatment.

Kline is nonetheless proud of his bill and believes it will reduce court congestion. He also boasts that he was able to pass “major legislation” in less than two years in the House while Mason has done “nil” in four.

Mason retorts that she cares not about being the prime sponsor, but about getting bills passed. Yet she takes care to note that she sponsored and passed legislation increasing financial aid for higher education. She also touts her ability to bring money to the district, declaring that she increased state Housing Trust Fund support for low-income housing from $250,000 to $10 million. That certainly would be an accomplishment, if true. But Mason’s numbers don’t check out: The trust fund spent $920,000 in the 37th in the year before she took office; last year it spent $1.7 million.

Effectiveness is measured in many ways, however. While Kline is generally regarded as being more willing to compromise to get legislation passed, Mason is valued by many for her outspokenness on controversial issues. She was one of the few legislators, for instance, to challenge the Seattle sports-stadium proposals. One Olympia insider calls her a “conscience.”

In the end, the vote may boil down to name recognition—bad news for Kline, since Mason has had more time in the public eye. When the dust clears, it’ll be interesting to see who’s still speaking to whom.