The chairman of the Senate Foreign Relations Committee says presidents should be sworn in earlier because the 2{ months between Election Day and Inauguration Day creates an unnecessary ``period of vulnerability.'' ``The incumbent president no longer has real political authority and the incoming president lacks constitutional authority, and the whole world knows it,'' Sen. Claiborne Pell, D-R.I., said Friday. ``It is a period of vulnerability which can and should be eliminated.'' In a Senate floor speech introducing a resolution for a constitutional amendment, Pell said the change would eliminate ``10 weeks of crippled leadership'' and avoid an ``unhealthy and unnecessary situation.'' The senator wants to move up Inauguration Day for the president and vice president from Jan. 20 to Nov. 20. The constitutional amendment also would move the swearing-in day for Congress from Jan. 3 to Nov. 15. Pell has introduced similar measures in the past. With time quickly running out in this session of Congress, action this year appears unlikely. From 1793 to 1933, the swearing in of new presidents took place March 4. The 20th Amendment pushed it back to Jan. 20 beginning in 1937. Pell, who introduced the resolution along with Sen. William V. Roth Jr., R-Del., said the move also would avoid `@lame duck'' administrations in which officials might be ``tempted to expend funds, make contracts and grants and promulgate regulations that may be either politically motivated or inspired by sheer self-interest.'' Pell said the development of voting machines and instant election result tabulations eliminates the justification for the long lag time between elections and inaugurations.