A new poll of likely Democratic voters in Congressional District 2 shows U.S. Rep. Ron Barber has a wide lead against his primary opponent, State Rep. Matt Heinz.

The Barber campaign commissioned the poll from Greenberg Quinlan Rosner Research, a Democratic polling firm used in the past by former U.S. Rep. Gabrielle Giffords.

The poll shows 77 percent of those surveyed supporting Barber and 13 percent supporting Heinz. The survey sample size was 200 likely Democratic primary voters, and it has a margin of error of about 7 percent.

Heinz says he's not surprised to hear Barber is well-known in the district because he just won election in which campaigns and outside groups spent $3 million, largely on campaign ads.

But Heinz questioned the size of the survey, saying it needed to be larger and have a margin of error closer to 5 percent to be more reliable.

Kate Kenski, who studies political communication at the University of Arizona, says the margin of error is within the range she would consider normal, and she says a sample size of 200 is small, but can be used to verify a wide difference in options, just as it was in this case.

Heinz also says the timing of the ad is problematic. The likely voters were surveyed July 17 through July 22. On July 23, Heinz began airing cable ads to introduce himself to voters, so he says the poll doesn't reflect the support he's gained since then.

"Starting July 23, my campaign has put up over 2,000 cable spots, so this poll is pretty much meaningless," Heinz says.

Barber's campaign says the favorable results support the positions Barber took during the CD8 campaign that ended with his election June 12. The wide margin does not mean the campaign is taking anything for granted, says Jessica Schultz, Barber campaign spokeswoman.

“We’re always going to run like we’re behind because we want people to understand the work that he’s committed to doing and why he wants to be in Washington representing the people of Southern Arizona," Schultz says.

The poll also had a second component, a matchup between Barber and Republican Martha McSally. McSally faces fellow Republican Mark Koskiniemi in that party's primary Aug. 28.

In that part of the poll, Barber led McSally with 53 percent of the respondents supporting him, to her 40 percent support.

The general election poll, commissioned by Barber's campaign from the same company and done on the same days, surveyed 500 likely general election voters and had a margin of error of 4 points.

Read the memo describing CD2 poll results: View at Google Docs | Download File

Your Vote 2012: The AZPM Election Center