State Sen. Scott Brown launched his second television ad Monday in the Massachusetts Senate special election.The 30-second spot seeks to paint Brown as a “regular guy,— driving around the state campaigning in a pickup truck as he seeks to “end business as usual in Washington.—Brown had held off making ad buys until last week, seeking to conserve funds in the runup to the Jan. 19 election. He announced on Dec. 31 that he raised $600,000 in December. He did not disclose his cash-on-hand total, but he had $515,000 in the bank as of Nov. 18.Democratic nominee Martha Coakley, the state’s attorney general, raised $1 million in the reporting period through the end of the year, her campaign said. She had $3.8 million in cash on hand as of Nov. 18.Coakley is heavily favored to win the race.