Whether it's because of admirable perseverance or sheer stubbornness, the current batch of Republican presidential candidates never say die. Not even a feeding frenzy of epic proportions can drive them out of the race, as we've seen in the past week with Rick Perry and Herman Cain. What might have been natural exit points for politicians in the past--developments that were unsettling, embarrassing, or worse--have had little or no effect.
There has been one major dropout: Former Gov. Tim Pawlenty of Minnesota withdrew in August after his campaign failed to catch fire. And former Gov. Sarah Palin of Alaska and Gov. Chris Christie of New Jersey considered running but decided not to.
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