Manhattan Borough President C. Virginia Fields, the highest-ranking black woman in city government, will soon announce she'll seek the 2005 Democratic nomination for mayor, campaign sources told Newsday yesterday. "She's running," a top adviser to Fields said on condition of anonymity. "She's got the fire in the belly. It's going to happen." Fields' entry into the race shakes up what is expected to be a crowded primary field that would include Brooklyn Councilman Charles Barron, ex-Bronx Borough President Fernando Ferrer, City Council Speaker Gifford Miller, Queens Rep. Anthony Weiner and City Comptroller William Thompson, who has said he'll announce his decision in the next week. Fields "poses a huge threat" to Ferrer, who has been hoping the two other black candidates, Thompson and Barron, drop out, said Baruch College political science professor Doug Muzzio. The news came as the Rev. Al Sharpton pointedly advised Ferrer, a former political ally, to make staff changes to alter the perception that his campaign is controlled by "Bronx machine" Democrats. [more]