Manhattan district attorney candidate Cy Vance Jr. - who lived in Seattle for 16 years - donated money to a Republican there who fought against gun control.
An examination of Vance's time in Seattle showed he gave $1,000 in 1998 to Christopher Bayley, a GOP Senate candidate who attacked the incumbent Democrat for supporting mandatory trigger locks and a ban on semiautomatic firearms.
Bayley, a former prosecutor in the Seattle area, sent gun owners across the state literature backing a proposal to let visitors to Washington state carry a concealed pistol if they had an out-of-state license.
Bayley also opposed abortion rights and supported a measure that would roll back state affirmative action programs.
Richard Aborn, one of Vance's opponents in the Democratic primary, jumped on Vance's support of Bayley, calling it wrongheaded.
"Manhattan residents can be assured that anti-choice, anti-gun control, anti-affirmative action zealots running for office will never have my support," Aborn said.
"We are significantly better off with the Democrat having won that election, and Mr. Vance and I simply have an honest disagreement about that," Aborn said.
Vance defended his support for Bayley as "appropriate." He called him a "very well-regarded" lawyer.
"If you look at my giving record, I think you will find that I am an active and repeat, almost recidivist, donor to Democratic candidates around the country," Vance said.
Aides said Bayley is the only Republican to ever received Vance's support. He has supported a slew of Democrats, including President Obama.
Vance, who is counting on Manhattan's liberal-leaning Democrats who typically vote in the primary to support him, moved to Seattle in 1988 to build a name for himself outside the shadow of his famous dad.
His father, Cy Vance Sr., was secretary of state in the Carter administration.
The winner of the Democratic primary on Sept. 15 is likely to win November's general election to replace longtime DA Robert Morgenthau.