DK:

Everything you say here makes sense except your statement that Obama could have spent time and money "putting McCain away early" instead of fighting off Hillary.  I don't think you ever put away a candidate early in a general election.  The Constitution fixes the date of the presidential election, and both candidats are stuck in the race until the end.  Primary candidates might quit early when they realize their chances are nil, but in the general there are only two candidates, meaning that neither will be finished until the fat lady sings. 

 So it's arguably better for Obama to wait a little before focusing his attacks on McCain.  That well they'll still be fresh on election day.  If he attacks McCain now, it will be old news by November.  

--Z