In a national exit poll of 800 voters conducted on my behalf by the polling company, inc./WomanTrend, 8 percent of respondents said that the definition of marriage was their top issue, while another 20 percent called it one of their three top issues.

Interestingly, 44 percent of voters said they would be less likely to support a candidate who supports same-sex marriage (including 32 percent who said they would be much less likely), while 40 percent said they’d be more likely (including 21 percent who said they would be much more likely). -- Human Events

The same poll that NOM participated in showed that 60% of Americans support marriage as the union of one man and one woman.