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Scott Brown Vs. Martha Coakley: A Primer

They've debated whether to call it "Ted Kennedy's seat" or "the people's seat," but a lot of observers seem to agree to call it a contest now -- it's the race for the Massachusetts seat in the U.S. Senate that'll be decided next Tuesday... one apparently tight enough now to draw the president up to this reliably blue state, to try to rally voters to the polls.

It's the middle of January and this isn't a time people are used to voting or surrounded by other political information, so we might normally expect turnout to be much lower than in a presidential election, and maybe lower than a midterm. (Public polling in the race has offered a mix of results. That uncertain turnout could make this a tougher place to poll, as voters vacillate on whether they'll go out, or the electorate becomes harder to estimate.)

It's become cliche in special elections to say turnout is key, but some cliches got that way because they're true.

Here's why it especially matters in Massachusetts: Democrats have a large advantage in the state -- but elections are won at the ballot box, not the counts on the rolls. So, if Democrats in the state have heretofore believed they didn't need to turn out because Martha Coakley, at left, was a shoo-in, she (and the president) will try to motivate them with the idea that she isn't.

One need only look recently to New York's Mayor Mike Bloomberg, who did win re-election recently but with a much lower percent than many observers had expected, perhaps, some said, because some backers figured he was coasting and didn't need their votes.

Statewide, there are three times as many registered Democrats as Republicans: 37 percent registered Democrats, or 1.5 million voters, compared to just 12 percent registered Republicans, or 490,000. That obviously gives Coakley more to work with among the registered partisans. And if they turn out in force, their votes could mitigate any losses Coakley takes among independents, if she suffers that.

On the other hand, that low percent of registered Republicans is somewhat misleading and should be considered carefully. There are of course more people who consider themselves GOP'ers than 12 percent -- even in lopsided races Republicans do better than their registration numbers: Republican presidential Candidate John McCain got 36 percent; the GOP challenger to Democratic Governor Deval Patrick got 35 percent; and Republican Mitt Romney won the governorship here in 2002.

(AP Photo/Winslow Townson)
We can get some ideas about the size of the voting from recent elections. As a baseline, start with the primaries for this contest, which were held in December and also on atypical dates for elections. 668,000 voters turned out for a contested Democratic primary (by comparison, out of 1.5 million registered Dems, or less than half) and 165,000 Republicans (out of 490,000, or around a third) for a less-contested race that Scott Brown, at left, won.

If everyone interested and willing enough to vote in that primary turns out again (a reasonable assumption) that's around 800,000 voters, or less than a quarter of the 4.2 million registered in the state, probably as a starting point. And assuming they vote their partisanship that starts Coakley off with an edge within that group. From there, each party will mobilize their get-out-the-vote efforts to get the more habitual-voting partisans who didn't happen to come out for the primary.

Taking a midterm election as a measure, around 2.2 million votes were cast in 2006. Although that might have been considered high at the start of this special election race, there's a chance it could go that high this time with all the interest and money now surrounding it. As overall turnout approaches that number, the mix might favor Democrats because they simply dominate the state, numerically. Yet Brown's fortunes could rest on those independents who disapprove of the current Congress' agenda (and health care plans) and those who think of themselves as conservative or routinely vote Republican, even if they aren't registered as such.

George W. Bush got just over one-million votes here in 2004; Deval Patrick's GOP challenger got 784,000 votes in 2006. When Mitt Romney won the state in 2002, he did it with just over one-million votes as well, also in a midterm-sized electorate.

So Brown's target is probably somewhere in that range. To do it, he'll need some Dems to stay home, great turnout from his half-million or so registered Republicans (from whom he can expect near-total support) and then a exceptional showing among the independents (probably needing to get six or seven in ten of them). Amidst all the talk of party advantages, it should be emphasized that independents still outnumber either party in the state.

Obama to Campaign for Martha Coakley in Massachusetts
Marc Ambinder: Why Obama Is Going to Massachusetts
Scott Brown Leads Martha Coakley in New Massachusetts Senate Poll
Could Massachusetts End Dems' Senate Supermajority?
More on the Race from CBS Station WBZ-TV in Boston

Anthony Salvanto is CBS News Elections Director.