The 22nd Amendment puts a term limit on the Presidency. Term limits deny the nation the opportunity to re-elect successful presidents.One purpose of elections is to reward or punish leaders for their performance. Since second-term presidents will not face the electorate again, they have an incentive to use their discretionary authority without fear of retribution. In other words, they are less accountable to the public.
The Amendment also reduces the political power of the president to unacceptable levels. The day after a president wins a second term, everyone knows he is an instant lame duck. At the moment of his highest experience and level of authority, the president's ability to shape the policy agenda is diminished because everyone knows when he is leaving office.