Especially if Scott Brown ends up winning the election on Tuesday, one lesson to take away from this race is the value of establishing a first impression. Due to Coakley's victory-lap vacation from active campaigning, Brown was able to get his message out somewhat unopposed. He was able to focus the Senate debate on a few key issues that played to his strengths. By trying to run a cheery, independent campaign, Brown was able to keep Coakley from casting the race solely as a Republican-vs.-Democrat grudge match on behalf of Ted Kennedy's memory. Instead, the race became about health-care, pragmatic bipartisanship, and the economy (among other issues). All of these favored Brown.
After Brown's image as a scrappy independent and as a brake on radical programs in Washington gained traction, Coakley seemed to have chosen the strategy of a negative assault upon Brown. There is a chance that this strategy of polarizing out the race could work. However, it might also be seen as a significant miscalculation about the mood of Massachusetts and the US as a whole. Both state and nation are increasingly tired of the politics of fear and resentment. Democrats were able to use the "Had Enough?" slogan (one coined by Newt Gingrich) very effectively in 2006 and as part of their 2008 repertoire. So much of the first year of the Obama administration has been defined by the relentless use of demonization---from attacks upon Rush Limbaugh to assertions that skeptics of Obamacare are like defenders of slavery to implications that the Republicans seek to perpetuate a holocaust. Inflaming animosities may be a successful tactic of distraction from the failures of the present, but the public does eventually tire of that torrent of wrath.
Part of what made Barack Obama's campaign a success was its overt emphasis on hope (even as a few fear-inducing digs were made). That optimistic glean helped satisfy the public's desire for an escape from the dead-ender partisanship they saw in Washington. Even if (especially if) the Obama administration has failed to deliver on this glean, the public hunger for a more affirmative politics has only increased.
Brown is very shrewd to be running such positive ads at this point in the campaign. Few voters want to have the bitter taste of venom in their mouths as they vote for a candidate right now. Brown's best hope is to run as a force for the way forward---not just against another person.