OCCUPATION: Mayor of Newark, N.J.
PREVIOUS APPEARANCES ON THE TIME 100: 0
PRO: The seemingly indefatigable Booker is using New Jersey's largest city as a lab for innovations in housing and small-business growth. His approval ratings bode well for his 2010 re-election campaign, and his national profile is growing.
CON: Crime was down in 2008, but further economic woes could send the numbers back up.
Next John Boehner