There will be a show of Democratic unity this afternoon in an effort to topple a longtime Republican state senator from Queens. One of the Democratic candidates, Albert J. Baldeo, will be withdrawing from the race and endorsing City Councilman Joseph P. Addabbo Jr. Two years ago, Mr. Baldeo was a little-known lawyer in Queens who came within 2 percentage points, about 900 votes, of defeating the longtime Republican incumbent, State Senator Serphin R. Maltese. And Mr. Baldeo achieved that with no support from the party organization in Queens and largely with his own money. But this year, Mr. Baldeo’s...