A very simple change; require that all voting for Federal office be done by approval voting. In every election you get to vote for as many candidates as you approve of, and you don't vote for any that you don't approve of.

The candidate with the most votes is the one approved of by the most people and it therefore the one best for the job.

That would really dilute the power of the parties, the power of lobbiest, the single issue campaigners.