Huckabee isn't the only person who has lurched in the far right during the Obama years. His presidency has been met with a level of pure hatred and seething that has forced many republican politicians to become more bombastic and emotional.
In the aftermath of the 2012 election there seemed to some level of admission on the part of republicans that the extremism wasn't good. We got the "GOP autopsy" which called for immigration reform, Bobby Jindal implored republicans to stop being "the stupid party," Sean Hannity suddenly came out for immigration reform, etc. But as expected, the ideas formulated by the party in New York and Washington were out of step with republicans elsewhere. They still hate Obama, they still think he has destroyed the country, etc. And they rode that extremism to more 2014 gains, and now the base seems to be demanding they ride that wave again for 2016.
Trump's populist appeal seems to be rooted in the realization that for all the talk of Obama being the weakest, worst president ever...he has enacted much of his agenda, and republicans in congress have failed to stop him. Republican voters are mad, and they want someone who can "win" for them. I've always wondered...what's the appeal of guys like Cruz, Rubio, and Paul for president? They haven't beaten Obama - in fact they've been beaten by him time and time again. And it'll happen again in a few weeks with the government shutdown fight over Planned Parenthood. Trump gets to talk about all the things he'd do, how he'd accomplish xyz, and he has convinced a lot of people. Ultimately I think Scott Walker will be able to pick up that mantle once Trump fizzles out. Walker has actually accomplished shit that republicans want to see done. They want someone who has beaten and humiliated liberals, and Walker is that guy IMO. Even though his electoral victories are pretty weak (hasn't won any races during a general election November).