The Fix provides a useful list:
Voters are voting in Massachusetts! Polls in the Commonwealth are open from 7 a.m. until 8 p.m. and conventional wisdom has gelled that state Sen. Scott Brown (R) enters election day as the slight favorite to pull an upset of massive proportions over state Attorney General Martha Coakley (D). As always in an election, there things we know and things we don't know. Here's a look at a few of the most critical knowns/unknowns.
What We Know: Independents are breaking heavily for Brown. What We Don't: By how much can Coakley afford to lose independents given the state's strong Democrat leanings? 60-40? 65-35?
What We Know: Democratic intensity/interest in the special election has improved considerably over the last few days. What We Don't: Does the fact that loyal Democrats are now more keen on turning out to vote make Coakley more competitive? Or are these people who would never have voted for Brown anyway?
What We Know: Millions -- upon millions -- of dollars have poured into Brown's campaign account over the past 10 days. What We Don't: With television time entirely sold out, can Brown smartly spend those dollars on get out the vote efforts? Or will millions go wasted simply because the financial piece of the race broke too late?
What We Know: National Democrats with a major assist from organized labor are going all out from an organizational perspective -- they have taken over every aspect of Coakley's campaign -- to save this race. What We Don't: Is everything national Democrats are doing too little, too late? Can organizational might save what has been, to put it mildly, a campaign with deep messaging problems?
What We Know: The broad swath of polling released over the last few days suggests that Brown has the momentum. What We Don't: How reliable any of this polling is given that there is no historical parallel for a Senate special election in January, making it extremely difficult to figure out who will vote and who won't vote.
ALSO NOTE: The Fix will be covering the heck out of the Massachusetts Senate race today so check back regularly for updates. Also, check out the Fix Twitter feed for more instantaneous updating.