Voters on the Upper East Side have the rare chance next Tuesday to help decide what kind of Republican Party New York should have. The candidates in the primary to face Gifford Miller to represent the 5th District in the City Council are Jennifer Arangio, a securities lawyer, and Douglas Winston, an analyst at the Human Resources Administration. Ms. Arangio is one of several candidates running on a new “Urban Republican Platform” that hews to core Republican principles like lowering taxes and removing barriers to building, without alienating New Yorkers by embracing national Republican causes on gay marriage or abortion. Mr. Winston, by his policy stances, is a Manhattan Republican in an older mold, one that is practically indistinguishable from the Democrats. At a debate hosted by one branch of the New York Republican Club last week, Mr. Winston mouthed vague truisms about “efficiency” when asked about how he would cut the size of government, while Ms. Arangio talked about much-needed privatization. Mr. Winston defended the rent control system that stymies building in this city and complained of overdevelopment, while Ms. Arangio favored dismantling rent control.

The Upper East Side used to be one of the few places in this one-party town where a Republican could get elected, but the lo cal party lost its way in the second half of the 1990s, eventually working to hew so close to Democratic positions that voters were offered only candidates’ personalities. Ms. Arangio faces a tough fight against the speaker of the City Council, but she is the kind of forceful, smart candidate who could make the first step toward rebuilding the party. She would have an even stronger chance of adding herself to the City Council’s three-member Republican minority if Mayor Bloomberg decides to withdraw his support for the Democrat, Mr. Miller.

That’s right. Our non-partisan mayor, perhaps suffering from the summer heat in June, actually declared of the Democratic speaker in an interview on New York One, “If [Mr. Miller] were in my district I’d probably vote for him. I think he’s doing a good job.” Since then the mayor, reeling from the tax revolt that is taking hold in Brooklyn and Staten Island in the wake of his 18.5% property tax increase, has made noises about repealing the tax hike. Mr. Miller has indicated that he would be a barrier to any such rollback. Efforts to gauge the mayor’s political astuteness will focus on whether he rethinks his position on how he would vote were he a resident of the 5th District. Mr. Bloomberg may want to ban political parties, but he’d do better to create a new, strong Republican Party on the shoulders of such potential stars as Ms. Arangio.