Rep. Steny Hoyer's (D-5th) decision to step down after 45 years in Congress set off a scramble among Democrats seeking to replace him, with 24 Democrats already raising and spending millions toward the June 23 primary. (Photo by Bryan P. Sears/Maryland Matters)Former U.S. Capitol Police Office Harry Dunn has raised more than $2 million in the crowded Democratic primary to replace long-serving U.S. Rep. Steny Hoyer (D-5th), while a free-spending…