OCCUPATION: Former Prime Minister of the United Kingdom
PREVIOUS APPEARANCES ON THE TIME 100: 1
PRO: Two years after resigning from office, he has kept himself busy as a U.N. envoy in the Middle East. But he might be of greatest use in increasingly volatile Northern Ireland, where he played a key role in the late-'90s peace process.
CON: Blair's approval ratings dipped to Bush-like lows by the end of his administration, and he has yet to make much progress in the Middle East.