Bush defeated a challenge from conservative commentator Pat Buchanan to win his party's nomination. Meanwhile, independent candidate Ross Perot, a billionaire businessman from Texas, emerged as a major factor in the race. Perot ran a populist campaign that focused on voters disillusioned with both parties, and he emphasized his opposition to the North American Free Trade Agreement and his desire to balance the federal budget. Polls taken in early June 1992 showed Bush leading the race, followed by Perot and then Clinton. From July to September, Perot temporarily dropped out of the race, causing severe damage to his candidacy. At the 1992 Democratic National Convention, Clinton chose Senator Al Gore of Tennessee as his running mate, and the successful convention helped unify Democrats behind Clinton. While the 1992 Republican National Convention placed a heavy emphasis on social issues, Clinton's campaign focused on the state of the economy, which was still emerging from the early 1990s recession.