Rep. Tim Walz (D) continues to maintain a double-digit lead over his opponent, according to polling data released by the campaign of physician Brian Davis (R) and the National Republican Congressional Committee.

The survey showed Walz had 50 percent and Davis had 32 percent, with 14 percent undecided. The Tarrance Group poll of 300 registered voters on Sept. 17-18 had a margin of error of 5.8 points.

In a memo, pollster Brian Tringali pointed to Walz’s 50 percent support as proof that the freshman Democrat is vulnerable.

The poll also pointed to presidential ballot as proof that the district is winnable for Davis. In the survey, GOP nominee John McCain led Democratic nominee Barack Obama, 45 percent to 43 percent.