An amendment to change the term of Congress, both houses, and the president to one 6 yr term, no reelections.
This would eliminate the powerful incumbents.
It would narrow the candidates down to those that truly want to help the country and its people.
It would eliminate the reelection campaigning, and keep the elected officials targeted to their job, instead of trying to get reelected. This saves money from the taxpayer as they won't have to subsidize these on the job campaigns.
Even if a representative tries to run for the senate, or the presidency, they would only be able to do it once. The same is true for a senator going for the presidency.
Currently, the president puts in two years in the first term, and then starts campaigning. This campaigning uses huge amounts of government resources, and campaigning is a full time effort, and that is a distraction from the job of being president.
Congress would be less likely to gridlock because there wouldn't be powerful incumbents to make a lock. The power of each congress would change, and in order to get something done, the members would have to work with the other party.
The current system has clearly failed, and that can be verified by looking back at what the previous congresses and presidents have accomplished, or more correctly not accomplished in the last several decades.