About 150 million. There are 207,643,594 eligible voters in the U.S. The census bureau estimates as of July have the US total population at 303,824,640. As of the 2006 general election the Voting Age Population (all adults) was 225,964,346 whereas the Voter Eligible Population (adults - ineligible people like felons or non-citizens) was 207,643,594.
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