The purpose of this AHC is to make all presidents of the US, started from 1940s or 1950s, up till present day - all of them started their electoral career in presidential election. They never ran in any other election previously (a previous failed bid for presidency is allowed), never hold any electoral office before their election as presidents. Basically, a president like Eisenhower.
POD can be anytime since 1900. The caveat is that it cannot be done by subverting constitutional order, which means no coup or revolution allowed.
Some ideas:
-More victory in wars and therefore more generals elected as presidents. Perhaps victory in Vietnam or other war.
-Technocrats become presidents:
Get some technocrats climbing the political ladder all the way to Cabinet positions such as Secretary of State, without going through electoral politics, and then become a viable presidential candidate. Remember all the talks about Condoleeza Rice?
-Tycoons
There are enough tycoons in OTL who think that they can do this, one of them is now in the realm of possibilities of moving into White House. In this board we got timelines of President Henry Ford, President Walt Disney etc. So why not?
-Mass movement leaders
Maybe leaders from Civil Right Movement, feminist movement, anti-war movement or even Tea Party movement throwing themselves to the ring and win!
-Celebrities!
President Kanya West, anyone?
The second part of the OP is WI. If this happens, what are the impacts on the US' politics, with more than half of century without governors and senators as Presidents? How would it affect the psyche of American public?