The kickoff ad repeats a clip of McConnell saying "I've lived on a government salary for 30 years" as the screen flashes details on his record, noting his votes to raise congressional pay, for the financial bailout and for cuts to Medicare.
"Mitch McConnellMitch McConnellProgressive group changes tone on Kaine Trump hits Kaine on TPP: He supports a 'job killer' Clinton maps out first 100 days MORE 'has long ceased to serve the state,'" the video reads, a quote from a blistering Courier-Journal editorial.
"After 30 years … it's time to switch."
It will be backed by a minimum $250,000 buy and will run statewide in Kentucky.
Senate Majority PAC's choice to make McConnell one of its first targets this cycle — it's spent heavily in the Massachusetts Senate race, but hadn't yet launched air attacks on incumbent Republicans — reflects the belief among Democrats that McConnell's one of the most vulnerable Republicans heading for reelection this cycle.
The groups cite Democratic polling that has shown McConnell to be one of the most unpopular Senators in the nation, and vulnerable to a potential Democratic opponent.
McConnell is aware of the target on his back, however — he's already gone on air with ads of his own, featuring his wife criticizing attacks from a progressive group, and he's been working to build his image as a fighter for Kentucky.
McConnell campaign manager Jesse Benton tied the new ad to previous attacks from Democratic groups and said the heavy Democratic offense may actually be improving McConnell's support.
""From office buggings, to racist tweets about Mitch's wife, to the constant stream of negative ads, Barack ObamaBarack ObamaDem donor irked by Nordic dinner invite Five decades of Democratic convention memories First lady goes to bat for Clinton MORE's allies are desperate to attack Senator McConnell at all costs," he said. "The increasingly unhinged attacks by Washington liberals only reaffirm Kentuckians' pride in Mitch McConnell for fighting to protect Kentucky from Obama's bad ideas."
National Republican Senatorial Committee spokesman Brad Dayspring suggested that Senate Majority PAC would frustrate incumbent red-state Democrats by spending on McConnell, which he said is akin to "lighting their resources on fire."
"Endangered red-state Democratic Senators like Mark PryorMark PryorCotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm Top Democrats are no advocates for DC statehood MORE, Mark BegichMark BegichSenate GOP deeply concerned over Trump effect Ex-Sen. Kay Hagan joins lobby firm Unable to ban Internet gambling, lawmakers try for moratorium MORE, and Kay HaganKay HaganDemocratic National Convention event calendar 10 Senate seats most likely to flip in 2016 Senate Republicans are feeling the 'Trump effect' MORE must be thrilled that Harry ReidHarry ReidDems put immigration front-and-center on convention's first day Dem ad blasts Indiana senate candidate on Social Security Super-PAC targets Portman on trade MORE's super-PAC is lighting their resources on fire in Kentucky rather than helping them to protect their seats from being lost," he said.
He also noted that Democrats have been unable to convince their top remaining recruit, Kentucky Secretary of State Alison Lundergan Grimes, to jump in the race.
"Though may be the most reluctant candidate in America, nonetheless Democrats are desperate to find a sacrificial lamb in Kentucky and if they want to burn their resources in the process that's just fine with us," he said.
--This piece was updated at 12:14 p.m. to clarify polling on McConnell's popularity.