The money quote for Dems for describing McCain's problem with impulsive decisions is from McCain's own 2002 autobiography, "Worth the Fighting For", where he says of himself:
"I make them (decisions) as quickly as I can, quicker than the other fellow, if I can. Often my haste is a mistake, but I live with the consequences without complaint."
(Source: this NYT article.) Living with the consequences of his own mistakes is fine, but can the country afford to live with the consequences of what even John McCain describes as the mistakes that often result from his hasty decision-making?
And let's not forget, the list of hasty decisions goes far beyond Palin, including his impulsive statements about the Georgia crisis, his gamble to cancel the first day of the convention so he could fly to New Orleans in case Gustav was another Katrina, and perhaps most important, Iraq.
After Sept. 11, McCain impulsively came to the conclusion that Iraq should be the first target! This shows worse judgement even than Bush! -- Bush at least first went to Afghanistan before abandoning that front for Iraq. Again, from a NYT article:
"There is a system out there or network, and that network is going to have to be attacked," Mr. McCain said the next morning [the morning of Sept. 12 2001] on ABC News. "It isn't just Afghanistan," he added, on MSNBC. "I don't think if you got bin Laden tomorrow that the threat has disappeared," he said on CBS, pointing toward other countries in the Middle East.
Within a month he made clear his priority. "Very obviously Iraq is the first country," he declared on CNN. By Jan. 2, Mr. McCain was on the aircraft carrier Theodore Roosevelt in the Arabian Sea, yelling to a crowd of sailors and airmen: "Next up, Baghdad!"
Updated: fixed link on source for quote.