Lawyers for imprisoned former Gov. Rod Blagojevich submitted an additional argument Wednesday to the federal court that’s considering his appeal, saying a recent U.S. Supreme Court decision bolsters their contention that the Illinois Democrat never crossed the line from legal political horse trading into corruption. Blagojevich, 57, is in his second year behind bars in a federal prison in Colorado serving a 14-year prison sentence for political corruption — including attempting to sell or trade an …