FRANKFORT, Ky. (AP) — Senate Minority Leader Mitch McConnell on Wednesday debuted a new campaign TV ad, featuring the whispery voice of a throat cancer survivor who credits the five-term Kentucky Republican for supporting sick workers at a uranium enrichment plant.

McConnell's campaign is spending "six figures" to air 30-second and 60-second versions of the ad across Kentucky, said campaign spokeswoman Allison Moore. She called it the campaign's largest ad buy so far in what's widely expected to be Kentucky's most expensive campaign ever.

McConnell faces a GOP primary challenge from Louisville businessman Matt Bevin, with Democrats awaiting the winner. The Democratic front-runner is Kentucky Secretary of State Alison Lundergan Grimes.

In the McConnell ad, Robert Pierce says he was diagnosed with throat cancer after being exposed to radiation while working at the Paducah Gaseous Diffusion Plant in western Kentucky.

He credits McConnell for helping provide cancer screening programs and compensation for sick workers at the plant, which for decades supplied enriched uranium to nuclear powers plants.

"He knocked down walls for us," Pierce said in the 60-second ad. "He helped save peoples' lives. ... I know firsthand, he cares."

Pierce worked at the Cold War-era facility for 26 years but was diagnosed with throat cancer in 1998 at age 43, the McConnell campaign said.

Pierce added in the commercial that McConnell "gets results for Kentucky that no one else can."

The comment plays up McConnell's seniority in the Senate, which the incumbent hopes is the trump card in his tough re-election campaign for a sixth term.

The ad also tries to deflect Grimes' portrayal of McConnell as a partisan obstructionist.

Grimes criticized McConnell for voting against a $1.1 trillion governmentwide spending bill last week. The measure sent to President Barack Obama eases the harshest effects of last year's automatic budget cuts.

The Democratic challenger said the bill would benefit Kentucky with features such as grants to promote business opportunities and investments in infrastructure, job training and early childhood education.

Grimes said the budget bill vote was another example of McConnell choosing "to work against the people of Kentucky." Grimes released her own jobs plan during a speech last week.

McConnell's campaign pointed to his support of the Paducah plant as an example of his work for Kentuckians. His campaign said the senator secured funding for a medical monitoring program for the Paducah plant workers and retirees, which included a mobile CT scan to screen for early stages of cancer.

McConnell also worked to provide compensation for sick workers, campaign officials said. As a result, those injured by radioactive materials became eligible for $150,000 in compensation and free health care for life, they said.

The Paducah plant's future seemed dim last year when U.S. Enrichment Corp., which leases the plant from the U.S. Department of Energy, said it planned to cease production and lay off most of the plant's approximately 1,100 workers. (U.S. Enrichment Corp. was the subject of a recent series by the Washington Examiner watchdog team called "Enrichment at the Public Till.")

But the Energy Department announced late in 2013 that it was entering negotiations with General Electric's nuclear division on a proposal to replace the aging plant with a new facility.

Kentucky's political leaders, including McConnell, Republican U.S. Sen. Rand Paul and Republican U.S. Rep. Ed Whitfield, pressed the Energy Department to clean up the plant in hopes of finding a new role for the facility and its workers.