December 23, 2004 Republican Plans Challenge to Bloomberg in Primary By MICHAEL SLACKMAN teve Shaw was once the president of his co-op board, the only elected office he said he had ever held, and now he wants to be mayor of New York City.Mr. Shaw, 30, an investment banker with a Canadian firm in Midtown Manhattan, is planning to run in a Republican primary against Mayor Michael R. Bloomberg.Mr. Shaw is young, a relative newcomer to the city, having moved here eight years ago, and is low on campaign money, but he does have a Web site, a few thousand...