The tipping point may finally have been reached. According to the newest USA Today/Gallup poll, more Americans now hold Barack Obama responsible for the lousy econonmy than his predecessor:

Eight of 10 say the economy is in a recession, and nearly as many say it hasn't improved over the past year. Even more ominous: Six in 10 predict the economy a year from now will be the same or worse than today, a downturn from the public's views last year and the year before.

That gloomy outlook, economists say, can become a self-fulfilling prophesy.

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Former president George W. Bush deserves a great deal of blame, 36% say, a decline of 7 percentage points since mid-2009, five months after he had left office.

Twenty-four percent say Obama deserves a great deal of the blame, up 10 points since 2009. For the first time since he took office, a majority of Americans - including six in 10 independents - say he deserves a great deal or moderate amount of blame for the nation's economic woes.

"The blame-it-on-my-predecessor line is of decreasing help to an incumbent," says political scientist William Mayer of Northeastern University. "It was perfectly fine when he took office, and even reasonable a year or two in, but eventually, increasingly, it becomes Obama's economy. It won't surprise me if by the time you get to the 2012 election Obama has overtaken Bush in that regard."

Also, the IMF has downgraded growth projections for the US:

The International Monetary Fund sharply downgraded its economic outlook for the United States on Tuesday, projecting growth of an anemic 1.5% this year and 1.8% in 2012. Olivier Blanchard, chief economist for the international lending organization, warned that the world economy had entered "a dangerous new phase."

Obama will continue to use the "it's not my fault" line because he has no other choice. And he only has to convince 50% of the electorate that he's right.

But the effectiveness of the attack has been blunted considerably. Also, by this time next year, the public might not care who's at fault, they'll only be interested in results. For that, the GOP nominee will have to come up with specific plans that make sense to the voter.