I would normally write some kind of introduction to clearly setup my point, but none is needed. Thank you The American Conservative:
Walker’s decline isn’t really all that puzzling ... Once he started campaigning in earnest, the actual candidate did not compare well with the imagined version of Walker that so many of his fans had created from what little they knew about him from his tenure in Madison. He failed to live up to a version of himself that never existed, and the reality of Walker turned out not to be very interesting.
In other words, nothing “happened” to Walker. His weaknesses as a national candidate were there for all to see, but most Republicans preferred not to see them until Walker made them impossible to ignore. Many of his fans assumed that Walker’s poor grasp of foreign policy issues would be remedied over time, but instead he has just adopted the most hard-line positions he could find with no sign that he has thought seriously about any of them. It is often said that he has been hurt most by Trump’s presence in the race, but that is mostly because he has responded to Trump’s challenge in the most ham-fisted and clumsy way possible.