Because they're representatives of God's heavenly kingdom.

Serena Williams told reporters at Wimbledon on Wednesday that she's excited about Barack Obama's candidacy but won't vote for him because Jehovah's Witnesses "don't get involved in politics." Her sister Venus—who is also a Jehovah's Witness—wouldn't even comment on the presidential election. Why don't Jehovah's Witnesses vote?

Because of John 17:14 and other passages in the Bible. In that verse, Jesus says of his followers: "They are not of the world, just as I am not of the world." Jehovah's Witnesses have interpreted that statement as a call to remain neutr...al matters. (In some of the sect's literature, members are described as "representatives of God's ...ly kingdom"; they are thus obligated to stay out of local political affairs in keeping with the behavior of ambassadors.) Witnesses also refrain from serving in the military, running for public office, and pledging allegiance to the flag.

Voting is not expressly prohibited, but it is discouraged. The Watchtower, the official publication of the Jehovah's Witnesses, ran an article in 1999 suggesting that the decision whether to vote was one of personal conscience, although it carefully laid out reasons for staying out of the voting booth. In reference to countries that require all citizens to show up at the ballot box, the Watchtower has explained that "[w]here Caesar makes it compulsory for citizens to vote … [Jehovah's Witnesses] can go to the polls and enter the voting booths," but the Watchtower did not specify what Witnesses should do with the ballot itself. According to some, the requirement for political neutrality led to the violent persecution of Witnesses in Malawi during the late 1960s and early 1970s, when adherents refused to register with the ruling Congress Party.

Most Jehovah's Witnesses in America do, in fact, abstain from voting. According to a survey released this week by the Pew Forum on Religion and Public Life, the religious group is far more likely than any other to believe that there is only one true way to interpret religious teachings. In keeping with that adherence, just 13 percent reported they were registered to vote.

While Witnesses have shied away from electoral politics, they have left a strong mark on the judicial branch: The group has brought several dozen civil-liberties cases before the Supreme Court, including a famous 1943 case over whether Jehovah's Witnesses could be forced to recite the Pledge of Allegiance in schools.

Jehovah's Witnesses are by far the largest religious group that refuses to vote, but they are not the only ones: Old Order Amish, Christadelphians, and Rastafarians have all traditionally shunned politics. (In the case of both the Amish and the Rastafarians, though, attitudes have changed a bit in the last few years.) Nationally, about 2 percent of people...er to vote cite religious reasons. If Jehovah's Witnesses did vote, they probably wouldn't form a large bloc anyway: the group makes up less than 1 percent of the U.S. population and is widely distributed across the country.