With recent polls showing a growing gap between Senator McCain and the surging Democratic rival, Senator Obama, the presumptive Republican nominee is looking for additional support from an unlikely source: New York City Democrats.

The McCain campaign will hold an open house at a Brooklyn Heights home today specifically for Democrats who want to vote Republican, as part of its efforts to advertise Mr. McCain’s bipartisan appeal.

The event will be held at the home of the former chairwoman of Environmentalists for Clinton-Gore 1992, Roberta Weisbrod, a Democrat who is now supporting Mr. McCain.

“Almost everybody I know doesn’t feel the way I do,” Ms. Weisbrod said, adding that her neighborhood leans predominantly to the left. The Arizona senator “always seems to take principled positions on a lot of issues.”

Ms. Weisbrod said attendees of today’s open house have been identified by Mr. McCain’s staff as Democrats interested in becoming active in the campaign or those who just want to know more about Mr. McCain’s platform.

Speakers at the event, which begins at 6:30 p.m., include the chairman of Mr. McCain’s New York campaign, Edward Cox, and a former campaign manager for President Carter, Robert Kennedy, and Senator Kennedy, Bartle Bull. Mr. McCain will not attend; he will be appearing at a town hall meeting in Nevada.

“In New York, we are finding that there is a groundswell of support by Democrats who are fundamentally uncomfortable with Obama and coalescing around John McCain,” a spokesman for Mr. McCain, Peter Feldman, said.