Do Congresscritters have to get clearances? Or is that also just conferred by the job?
Technically speaking, a clearance can be granted without any background check or time limitations. It's just extremely friggin rare, and pretty much exclusively due to political intervention. On the flip side, a clearance can be revoked without cause or warning.
The President is automatically assigned the highest possible access. It comes with winning the election. The standard "Above Presidential security clearance" is Hollywood BS. There are no secrets, military or overwise, that the President does not have automatic Need To Know. The counter weight to this is impeachment, and that's about it.
On the flip side, Congress is required by the Constitution to handle all funding. Since all government activities cost some amount of money, they also have Need To Know on any classified projects. Because the projects have some cost. Making the entire Congress aware of the black budget would be a very bad idea. So we have groups such as the Senate Select Committee on Intelligence(
Link). I'm not 100% positive, but I do believe requiring security clearances for the SSCI and such groups is un-Constitutional as it violates the seperation of powers. You cannot have the Executive branch being able to hold security clearanes over the heads of the Legislative branch that controls the Executive budget. Ergo, we the people provide the necessary 'clearance' for the Congresscritters. In practice, Congresscritters police themselves on such things through committee membership.
However, un-elected staff members and such do require security clearances.