Watch Pima County, the second largest after Maricopa. Obama is likely to win the county by a large margin. If he's going to win the state, and assuming that McCain takes Maricopa by five points or so, Obama will need a margin that is about 20 points over McCain, a tall task, but doable if turnout is very high. As of '06, Maricopa had 3.8 million people living in it; Pima had just under a million. (The margins cancel if turnout rates are equivalent in the two counties. )
Of course, it might be a long night in Pima County... local journalists expect delays and vote counting issues.
Arizona's other 13 counties have about 1.4 million people in it; if Obama can come out ahead here, tied or just a little behind, he could have a real shot, providing, again, that he does very well in Pima and loses Maricopa by fewer than five points.
In any event, a reader sends in a scenario where Arizona would matter:
McCain draws to a straight flush and wins PA, for a net pickup of 21 (these people who say "draws to an inside straight" don't understand poker odds: that's not that unusual!)
2. Obama wins VA (+13), IA (+7), NM (+5), CO (+9), for a net pickup of 34.
In this case, Obama would be 5 short of 270 (Kerry=252, losing PA=-21 => need 39 to win). He could pick them up from NV (+5) or AZ (+10). You could also assume that McCain draws a second straight flush, winning NH. In this case, NV isn't enough: Obama needs AZ, with or without NV.
The scenarios are unlikely, but Obama's somehow losing PA but winning Ohio or Indiana is even less likely. (Would he win AZ if he lost CO or NM? Not likely.)
The Obama campaign continues to appeal for help in AZ, although some Arizona Obama supporters are getting e-mails urging them to drive to New Mexico and make phone calls to voters in Pennsylvania.
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