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PLATTSBURGH, N.Y. -- The rise of conservative "tea party" activists around the country has created a dilemma for Republicans. They are breathing life into the party's quest to regain power. But they're also waging war on some candidates hand-picked by GOP leaders as the most likely to win.

In upstate New York, Dede Scozzafava, 49 years old, is the choice of local party leaders to defend a Republican seat in the U.S. House of Representatives, an abortion-rights candidate who could appeal to independents. Doug Hoffman, 59, is a local accountant backed by tea-party activists who has jumped into the race declaring himself the real conservative.

Mr. Hoffman has siphoned so much support from Ms. Scozzafava that their Democratic rival has vaulted into the lead, according to a poll released Thursday. The election is Nov. 3.

"I am not your run-of-the-mill politician, and maybe that's why the Republican bosses didn't like me," Mr. Hoffman told a recent health-care forum sponsored by the Upstate New York Tea Party. In an interview, Ms. Scozzafava acknowledged her discomfort at the event. "I knew it wasn't going to be an easy audience for me," she said.