An internal poll conducted for the campaign of retired Air Force Col. Martha McSally found the Arizona Republican had a slight, within-the-margin-of-error lead over Democratic Rep. Ron Barber.  

McSally led 45 percent to 42 percent, with 13 percent undecided. The margin of error was 4.9 points in the OnMessage Inc. poll obtained by CQ Roll Call.  

The pair are locked in a rematch of 2012, when Barber narrowly defeated  McSally, and they are likely to stay close in the polls heading into November in this swing district. The poll showed similar numbers to one the same Republican firm conducted in June . Commissioned by the National Republican Congressional Committee, that poll found Barber ahead, but within the margin of error.  

Forty percent of respondents in the latest poll had a positive view of President Barack Obama, while 53 percent viewed him negatively.  

The campaign declined to release candidate favorability ratings or name identification figures. Both candidates should be relatively well-known — this is the third congressional bid in the past two years for both Barber and McSally, who ran in a June 2012 special (McSally lost in the GOP primary) before facing off in November.  

This is one of the most competitive House races in the country and is rated a Tossup by Rothenberg Political Report/Roll Call. At the end of March, Barber had $1.2 million in cash on hand and McSally had about $850,000.  

Wes Anderson and Kayla Sulzer conducted the poll for OnMessage Inc. It was a live interview telephone survey of 400 likely general-election voters fielded April 14-16. Thirty-seven percent of those surveyed said they were Republicans, while 36 percent stated they were Democrats.  

Here is the full polling memo:  

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