Left-handed people constitute about 10-15% of the U.S. population. Barack obama is left-handed. With the election of Barack Obama, we will have had 6 left-handed Presidents since World War II. William Jefferson Clinton is left-handed. George H. W. Bush is left-handed. Ronald Reagan was left-handed and was forced to write with his hand as a child. Gerald Ford was left-handed. Harry Truman was left-handed. Roosevelt, Eisenhower, Kennedy, Nixon, Carter, and George W. Bush were or are right-handed. So, of the 12 post-war presidents, half were or are left-handed (Source).

So, is there a vast left-handed conspiracy going on, at least for politicians? Note that John McCain is a left-hander (Source). So, what are the odds that we would have two left-handed presidential candidates. Let's say that 10% of the U.S. population is left-handed. The odds that both candidates will be right-handed is 9 x 9 or 81%. The odds that one candidate will be right- and the other left-handed 9 x 2 or 18%. The odds that both will be left-handed will be only 1%. Four of the last five presidents were left-handed. If McCain had won in 2000 and Kerry had won in 2004, six of the last six president would have been left-handed. Kerry is left-handed except that he throws with his right. The above are all statistically highly improbable, suggesting that there is a strong selection factor for lefties to run for and to become President of the United States, at least in the last 50 years.