From left, Scottie Mayfield, Chuck Fleischmann

Three weeks after promising to abstain from "negative" campaign advertising, Scottie Mayfield this week launched an attack ad condemning U.S. Rep. Chuck Fleischmann's voting record -- a record Mayfield praised as recently as May.

On July 5, after warning on Twitter "that we'll be attacked on TV soon," Mayfield spokesman Joe Hendrix told the Chattanooga Times Free Press that "Scottie committed to not going negative in any way."

But Mayfield is the first 3rd Congressional District candidate to use television to target a rival, and opponents say the dairy executive's latest ad proves he broke a campaign pledge to stay positive.

"This is what happens when a desperate campaign sees the race starting to slip away," Fleischmann campaign spokesman Jordan Powell said.

Hendrix indicated the ad was "the truth."

"Mr. Fleischmann is attacking Scottie instead of addressing the facts," he said.

As sinister music plays over black-and-white video of President Barack Obama, the Mayfield ad's unseen female narrator notes that "our congressman voted one out of four times with Obama."

There's more to the story. The ad's "one out of four" claim is based on a Congressional Quarterly study in CQ Weekly that examined 2011 House votes "on which the president took a clear position." According to the study, Obama took a clear position on 95 House votes in 2011. The House voted 945 times that year.

On those 95 votes, Fleischmann sided with the president 24 percent of the time. Other prominent conservatives had similar scores. U.S. Rep. Paul Ryan, R-Wis., and House Majority Leader Eric Cantor, R-Va., each voted with Obama 26 percent of the time, according to the study.

Fleischmann's 24 percent tied with U.S. Reps. Diane Black and Marsha Blackburn, both Tennessee Republicans.

House Republicans, known for stalling much of the president's agenda, averaged a score of 22 percent overall.

That's tied with Republican cooperation during Democrat Bill Clinton's administration. It's the lowest cooperation rate Republicans have had with any president since Eisenhower in 1954, the study said.

Among other matters, Fleischmann agreed with the president on three votes on free trade agreements with Colombia, Panama and South Korea. The congressman also voted twice to extend expiring provisions of the Patriot Act, echoing Obama's position on the issue.

All five votes passed the GOP-controlled House.

Fleischmann spokesman Powell criticized Mayfield's actions.

"The idea that Chuck has voted with President Obama is absurd," Powell said. "In fact, another opponent in this race [Republican Weston Wamp] has attacked him for being too harsh on President Obama."

Hendrix, the Mayfield spokesman, said Fleischmann "is out of step with other East Tennessee Republicans," noting that U.S. Reps. Phil Roe and Jimmy Duncan earned lower percentage scores.

"Except for procedural votes, we see little reason to ever agree with a president who demonizes free enterprise and small-business owners," Hendrix said.

Fleischmann campaign officials dismissed Hendrix's comments as disingenuous, pointing to Mayfield's May 14 speech at Hamilton County Republican Party headquarters in Chattanooga.

"I haven't studied [Fleischmann's] votes enough to tell you that I would vote significantly different," Mayfield said at the time. "He has voted conservative, and I praise him for that."

Republican Ron Bhalla; Democrats Bill Taylor and Mary Headrick; and independent candidate Matthew Deniston also are in the race.

Primaries are Aug. 2.