I'm happiest when all the polls in a race match up. It means we have a very good idea of how a race is going for the candidates in it.
So, naturally, I'm not happy about the Massachusetts Senate race right now. Seeing a 10 point swing from poll to poll, giving both candidates opposing 5 point leads, means we have to dig deeper to figure out what's going on.
I'm reminded of March of 2010 here. Here we go again with Rasmussen's likely voter polling (500 LVs, MoE 4.5) putting Republican Scott Brown ahead 49-44, while PPP's registered voter polling (936 RVs, MoE 3.2) has Elizabeth Warren up 46-41.
Rasmussen's details are behind a paywall, but that's the older poll anyway (2/29 vs PPP's 3/16-3/18). So I'll focus on the PPP's specifics to see what we can make of it. First, the poll asked about the voter's 2008 Presidential vote. A whopping 11% claim they don't remember or voted for someone other than John McCain or Barack Obama. That's a rather high number when the actual fraction that voted for someone else was just over 2%.
Between Obama and McCain, the actual two party vote was Obama 63.2, McCain 36.8. In the poll, the two party vote is Obama 64, McCain 36. So the poll favors Obama voters slightly more than the actual 2008 electorate did, but it's very close. Which is odd, as turnout was far from 100%, with 3 million votes cast of 4.2 million registered voters, for a registered voter turnout of about 71%. PPP seems to project that the 30% who don't vote have no particular lean.
Further, in 2008 the partisan registraion went 1.6 million Democrats, 0.5 million Republicans, and the rest other or independent, a split of 38 D/12 R/50 other. The poll shows 41 D/14 R/45 other or independent. That's outside of the Margin of Error for the Democrats. PPP seems to project that Massachusetts has grown more partisan and leans more toward the Democrats now than 4 years ago.
So if we believe PPP's projections of the partisan make up to hold true, and that there's no partisan lean in who votes or who doesn't vote, then Warren could be ahead in this race, despite the three previous polls all putting Brown ahead.
But right now PPP looks like the odd man out.