Washington (CNN) -- In President Barack Obama's two presidential campaigns, his predecessor loomed large; Obama and Democrats regularly laid the blame for the downtrodden economy at George W. Bush's feet. When pressed on their pledge to turn the faltering economy around, Obama and Democrats often pointed out that they had inherited the product of the Bush administration's policies. Bush, however, in his limited public appearances has stayed mute about his successor, maintaining a custom among former presidents that dates back decades. While not all presidents have adhered to the practice, it has created a mostly amicable brotherhood of former presidents.
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Former presidents regularly hold their tongue when asked about their successors
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"I don't think it does any good," George W. Bush said when asked about Obama
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Jimmy Carter hasn't adhered to the rule and regularly critiques Democrats and Republicans
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Dwight Eisenhower is considered the gold standard for working with a successor
Gergen said he feels @placeholder's silence about Obama stems from how Bush was treated in his last few years in office.