The Washington Post said its survey found 52 percent of Maryland voters approve of same-sex marriage and 43 percent oppose it, suggesting the state could be the first to adopt same-sex marriage through the popular vote.
Same-sex marriage is legal in six states and the District of Columbia due to legislative action and court rulings.
The issue is also on the Nov. 6 ballot in Maine and Washington state, where polls indicate majority support, the Post said.
However, the newspaper noted, pre-election polls have historically underestimated opposition to same-sex marriage and opponents of this year's ballot questions are expected to mount aggressive ad campaigns between now and the election.
The ballot question in Maryland -- Question 6 -- is a challenge to a law passed by the Maryland General Assembly that opponents succeeded in bringing to referendum.
The random sample of 934 registered voters and 843 likely voters was conducted by telephone Oct. 11-15, using both landline and cellphones, and was conducted in English and Spanish. The margin of sampling error is 4 percentage points for both samples.