In recent weeks, President Obama has demolished any expectations that he would seek re-election by returning to his idealistic rhetoric of 2008, when he promised to heal America's political divisions.

Instead Mr. Obama shrilly insists his Republican opposition puts party ahead of country with policies that would "fundamentally cripple America." He pits American against American on the basis of their bank accounts, saying it's time for "millionaires and billionaires" to "pay their fair share."

And he's again turning to preposterous straw man arguments, such as when he told Congress earlier this month that Republicans would "just dismantle government, refund everybody's money, and let everyone write their own rules, and tell everyone they're on their own."

Mr. Obama's attacks are not just at odds with his 2008 campaign's lofty tone. They are also politically dumb.

True, the president runs little risk of losing Democratic votes next fall. Some in his party are less enthusiastic about donating or volunteering than they were in 2008, but they will still vote for him. The Sept. 18 Gallup poll shows 88% of Democrats favoring him over Texas Gov. Rick Perry and 85% over former Massachusetts Gov. Mitt Romney. These are relatively strong numbers.

Karl Rove is a former senior adviser and deputy chief of staff to President George W. Bush. He is a Fox News contributor and author of "Courage and Consequence" (Threshold Editions, 2010). To continue reading his column in The Wall Street Journal, click here.