Analyzing history: What factors, voting trends tilt presidential elections?

(MEDIA GENERAL) — Ever wonder how political scientists — and the campaigns, for that matter — determine how states will vote in presidential elections?
What demographics are they looking at? What statistics tell us who is likely to vote for whom?
Political scientists and pollsters do this by studying voter trends, which are carefully identified and studied to try to determine which personal affiliations and demographic qualifiers can help predict which way a specific person is