# A Back of the envelope calculation

Rasmussen did some exit polling today. He found that 22 percent of Massachusetts Democrats voted for Scott Brown. If Democrats are 36 percent of voters (which is their representation among those registered to vote), then Brown captures 8 percent of the total vote just by virtue of Dems.
If he wins 11 of out of every 12 Republican votes, that would give him another 11 percent of the total vote (Republicans are 12 percent of registered voters). This would leave him needing another 31 percent of the total vote to reach 50 percent, which I take to the magic number given that the third party candidate will pick off some votes.
Brown could accomplish this by winning 62 percent of independent votes. Independents are a little more than 50 percent of registered voters, so winning 62 percent of their votes would get him a little more than 31 percent of the total electorate, thus getting to 50 percent by virtue of the following formula:

8 (Democrats) + 11 (Republicans) + 31 (independents).

But if, as has been reported, the percentage of registered Republicans (or registered Independents) who turn out exceeds the percentage of registered Democrats who do so, then the above calculations shift in Brown’s favor. That is, he won’t have to do quite as well among Republicans and independents if these cohorts vote in disproportionately large numbers.
It should also be remembered that Rasmussen’s exit polling of Democrats might not present an accurate picture. Exit polling can be rather inexact. 22 percent sounds about right, though.
UPDATE: Half the vote has been tabulated. Brown is in the lead 53-47.
If only Michael Barone were on television analyzing precinct results, we’d probably know the outcome for sure by now.
UPDATE: With 70 percent of the vote in, it’s Brown 53, Coakley 46. The gap in total vote is just about 100,000. Maybe we don’t need Barone at this point.
VICTORY!: Brown is being declared the winner by multiple outlets. I understand that Coakley is about to concede.