WASHINGTON — Republicans say open races in states where a Democrat is retiring offer them the best chance to increase their Senate majority. Sen. Elizabeth Dole, R-N.C., head of the National Republican Senatorial Committee, offered an upbeat perspective on the 2006 races Monday. The GOP holds a 55-44 advantage in the chamber, with one Democratic-leaning independent. Dole cited Minnesota, where the party has a single candidate, Rep. Mark Kennedy, running against a number of Democrats hoping to replace retiring Democratic Sen. Mark Dayton. The same is true in Maryland, where the GOP is backing Lt. Gov. Michael Steele, while several...