CHATTANOOGA (WRCB) - Bill Haslam still has a double-digit lead for the Republican nomination for governor while more undecided voters have apparently made up their mind since the last statewide poll.

The Mason-Dixon poll was conducted for the Tennessee Newspaper Network which includes WRCB partner Chattanooga Times Free Press as a member.

The scientific poll asked 400 likely Republican voters who they will choose in the August 5 primary.

Haslam picked up 36% support followed by Zach Wamp at 25% and Ron Ramsey at 20%. However, 17% of likely voters say they are still undecided. 

Just a few weeks ago, the number of undecided voters was larger than the support for any candidate. That has now changed significantly following the statewide NBC debate, increased campaigning, and heavy advertising.

A poll conducted by WSMV-TV (NBC) in Nashville found 36% of voters undecided the first week of July. Haslam was favored by 32% at that time followed by 21% for Wamp and 11% for Ramsey. Ramsey has seen the greatest growth in support since the WSMV poll but still trails Haslam and Wamp in name recognition, according to the poll.

Republican voters will decided their nominee on August 5. The winner faces Democrat Mike McWherter.