The danger of underestimating Walker is a common theme among the candidates and operatives on the losing side. Another senior Democratic adviser in one of Walker’s statewide races warned that his foes shouldn’t be lulled by Walker’s uneven start in presidential politics.

“He’s got antennas,” said the adviser, who also requested anonymity. “He’s the real deal. As time goes on, you’ll get more of that vibe as you cover him. He can come across as a little arrogant, obviously. But with real people out there, he’s really, really good. He’s just in touch with what they’re looking for.”

Walker’s opponents remember him as so unflappable and message-disciplined that he rarely created a stir. He was always polite behind the scenes at debates, said Lena Taylor, who said she appeared jointly with Walker 24 times when she tried to oust him as county executive in 2008, only to lose by close to 20 percentage points. Others recalled their off-camera interactions with Walker similarly. He’d always talk about his family, chitchat about the Packers or the Brewers sports teams, never say anything antagonizing.