f Governor Mitt Romney has a ''machine gun'' aimed at Democratic state lawmakers, as House Speaker Thomas M. Finneran warned last week, then the special House election in a district south of Boston offers Romney his first target. With six days left before voters go to the polls in the only state election this year, Romney and the state Republican Party already have poured considerable effort and money into the race. According to GOP executive director Dominick Ianno, the party has spent more than $10,000 on 24-year-old Matt Sisk's campaign, funding four mass mailings, two automated phone blitzes, and a...