Barack Obama - 46% (+5)
Rick Perry - 39% (-5)
That's a ten-point swing overall. The Obama number is particularly telling, because when Rasmussen tests candidates, the more unpopular ones produce a higher support number for the president -- independents ducking for the safety of the incumbent they like personally but wish was better at his job. Obama soars to 50 percent against Palin, 48 percent against Bachmann. Against Romney and Ron Paul (!), he's at 40 or lower.
It's only one pollster's trendline, but right now the scenario in which the conservative Southern governor doesn't win the GOP nomination involves 1) obscure ideological hiccups, like the HPV story, becoming more problematic, and 2) a preponderance of Republican voters believing that Perry is unelectable. It's just assumed that Perry would have a tougher time beating Obama than Romney would; all polls like this go into the magical narrative machine.
*and other people