As Democrats gather in Denver, commentators are starting to tire of Barack Obama's "change" mantra. Paul Krugman devotes today's column to the need for Obama to attack John McCain. Joe Klein worries that Obama is failing "to define his opponent" and failing, "in all but the most amorphous ways, to define himself." Republican strategist Mike Murphy writes that "many of the old-school party regulars now assigned to loyally wave HOPE and CHANGE signs for the TV cameras in Denver would dearly love to see Obama switch out some of his 'together we can' endive salad for a big populist pile of economic red meat." Last week E.J. Dionne wrote that many Democrats worry Obama lacks "a compelling narrative about how Americans who now feel economically insecure will find their way toward greater confidence." And in an excellent piece in yesterday's New York Times Magazine, David Leonhardt writes, Obama "still hasn't quite figured out how to sell it. For all his skills as a storyteller and a speaker, he has not settled on a compelling message about how to put the economy on the right path." Clearly the political class is tiring of Obama's message of "hope and change." But how about the voters? Most will just begin to tune into this election this week. But the latest poll numbers suggest that, for those who have been paying attention, the ch-ch-ch-changes message isn't gaining any traction either.