Though Michigan and Arizona will award roughly the same number of delegates tonight (with both losing half their original allocations for non-compliance with RNC calendar rules), and though Arizona will provide the larger "purse" by virtue of a statewide winner-take-all system, Michigan will get the lion's share of attention simply because it is by far the closer race, and is Mitt Romney's native state. The major drama will be all about Rick Santorum's bid for an upset there.
All the late polls in MI show a very close race, with Santorum's original lead yielding to a TV-fed Romney surge, and then a Santorum comeback, apparently on the strength of Democratic and independent voters (with the former including at least some "tactical" or mischief-making ballots cast by people who wouldn't normally support Rick for dogcatcher).
I find myself at the point where I feel it doesn't matter. Romney, Santorum — Obama is killing both of them in the polls. Unless the economy goes seriously south, or gas prices skyrocket to $6.00/gallon, this election is over.
But I'm told I shouldn't get complacent.