We live in a technological age so we could try this.
Each member of Congress is fitted with an explosive collar the day they assume office.
An ongoing Approval Survey is continuously by a neutral agency, say the NRA...ok...so they can't have the job.
When your approval rating falls below a certain, to be determined, % (maybe 60%?), the collar gives a beep and a slight tingle to the wearer.
Each day the rating is below the set %, you receive the beep and tingle as a reminder.
After a few weeks (number to be determined) of ratings below the %, the collar explodes and a special election is held.
The office holder can resign and have the collar removed at any time.
As an option, the voting could be done on a weekly Television show. where the contestants Congress-members can explain their performance.
At the end of the show, the results are tallied and signals sent to the collars.
Should a collar be instructed to explode, it will first relay it's location so the mess can be cleaned up with as little additional burden to the citizens as possible.
Edited as an after thought.
This will provide a popular vote on how the citizens "like" the member. Perhaps votes of those in the members state/voting region will count extra...maybe 2 instead of 1. This will allow some local support without taking away the necessity on severing the country.
Additionally. a Constitutional Judging Panel could be in place. 3 members strict, conservative, interruption, 3 members liberal interruption, and 3 members a neutral, or "on the fence" interruption. If this panel rules that you have violated the Constitution, it overrides the popular vote and you fail. ..... zzzzzzttt...booom
You must act within the Constitution before pleasing the electorate is even considered.