Nearly a third of Republican voters in a new survey say they would be less likely to vote for their party's nominee for Congress if the candidate were gay or lesbian. 

The Marist-McClatchy poll released Friday shows large majorities of each party say a candidate’s sexual orientation would make no difference in their vote. For Republicans, however, that majority is 67 percent.  

Eighty-four percent of Democrats and 89 percent of independents say a candidate's sexual orientation would not influence their decision. Some 13 percent of Democrats and 9 percent of independents say they would be less likely to vote for a gay or lesbian candidate for Congress; for Republicans, it's 30 percent.

The Republican Party has fielded a trio of gay candidates in races in Massachusetts, California and New Hampshire this year. If any of them prevail, they would be the first openly gay Republicans elected to Congress. 

Resistance to electing an openly gay or lesbian candidate is highest in the South and Midwest. 

The poll also found 51 percent of voters believe the decision to legalize same-sex marriage should be made at the federal level. Another 44 percent believe it should be a state issue. 

Overall, 54 percent favor same-sex marriage. 

The poll surveyed 1,035 adults from Aug. 4-7 and has a margin of error of plus or minus 3 percent.