Incumbency.

Don't like the fact that so many Congressmen get reelected term-after-term? What's the solution, you ask? Term limits has been the usual answer. It worked well for the presidency, certainly.

But perhaps a better system would be to prevent sitting Congressmen from ballot access. Which would mean a given Congressman can be reelected as many times as he'd like, but he cannot appear on the ballot for so long as he is in office. The beauty of this is to allow those individuals who are truly noteworthy politicians to spend quite a bit of time in Washington, while at the same time preventing the stagnation and tyranny that results from the current lifer system. It would also discourage public servants, being paid to govern the country, from moonlighting as campaigners. And lessen the use of public funds intended for legitimate government purposes--e.g. transportation for Senators desiring to address their electors--from being co-opted for illegitimate personal purposes. Of course, a given Congressman could serve back-to-back terms, but only if he wins his write-in campaign. Neat, no?