“He walked into a trap you could see 100 yards away,” said Grant Woodard, an attorney and longtime Iowa Democratic consultant unaligned with a candidate. “It does directly call into question people’s concerns: Should you really be the front-runner? Are you really electable?”…

“The challenge with mistakes, small or big, is when they play into what a candidate’s perceived vulnerabilities are,” said Jen Psaki, a longtime Democratic consultant who worked in the Obama administration. “Does it play into this building perception or criticism that Biden is not up to the task?”

“Ten years ago,” she added, “nobody would have asked that question.”

Mitt Romney’s comment that “corporations are people too, my friend” fed the narrative that he was an out-of-touch plutocrat. John F. Kerry’s comment that he voted for the Iraq War before he voted against it perfectly encapsulated the idea that he was a flip-flopper.

Gov. Rick Perry’s “oops” moment solidified an impression he was less intelligent than his political rivals.