Democrat Denny Heck is within the margin of error with Republican Jaime Herrera, according to an internal poll conducted for the Heck campaign and obtained by Roll Call. While Heck's poll finds Herrera at 47 percent and Heck at 44 percent, it's an improvement from recent public surveys and past polling conducted for Heck's campaign. The Greenberg Quinlan Rosner survey of 502 likely voters was taken Sept. 7-9 with a 4.4-point margin of error. Automated polls conducted by Survey USA found Herrera ahead by 13 points in August and 9 points in September. In June, a GQR poll conducted for Heck found him behind by 7 points. As the polling memo points out, Heck's positive movement occurred as outside conservative groups, including American Future Fund and Americans for Prosperity, have dropped hundreds of thousands of dollars in TV ads against him. Heck and Herrera are running to replace retiring Democratic Rep. Brian Baird, who won his last four races with more than 60 percent of the vote. President Barack Obama carried the district in 2008 with 56 percent.