Edit: By “overthrow” I mean an actual attempt to topple the government, not wandering around aimlessly in a building for 4 hours stealing furniture.
If you actually oppose power you would almost certainly be FBI’d long before you could ever get to a position where you could conceivably stage a coup.
Being barred from election is a very quaint punishment for leading a failed coup.
Life peers have the closest thing to no political power at all. The Lord's only purpose these days is to delay legislation and force review of bills.