Of all the above-mentioned billionaires identified by Forbes, only Oprah Winfrey qualified for Forbes 2009's list of the world's 20 most powerful billionaires, a list which considered not only wealth, but also market sway and political clout. Winfrey was considered especially powerful because of her influence on American consumer choices and her pivotal role in Barack Obama's successful 2008 U.S. presidential campaign.[10]..