The ad, "Cards," is a joint effort with Connecticut's Future PAC, a group formed in July that lists Joseph Taborsak, a Connecticut state Democratic lawmaker, as its treasurer. It's the first expenditure from Connecticut's Future this cycle.

The ad features a dealer laying down playing cards with photos of McMahon, families, a small jet and a large home while the narrator describes her tax plan as cutting taxes for millionaires to the detriment of the middle class. The narrator then says McMahon threatened to eliminate the Department of Education.

"She's fixed the game against Connecticut's middle class," the voiceover says.

The senate race in Connecticut has received increased scrutiny and involvement from both parties as it's become increasingly competitive in recent weeks. An independent poll recently showed McMahon up by 3 percentage points over Rep. Chris MurphyChristopher (Chris) Scott MurphyOvernight Health Care — Presented by the Association of American Medical Colleges — Governors criticize Trump move on pre-existing conditions Bipartisan group of senators asks FDA to examine drug shortages Trump faces Father’s Day pleas to end separations of migrant families MORE (D), a feat she was never able to achieve during her losing 2010 campaign against Sen. Richard Blumenthal (D).

Majority PAC's involvement in the race indicates Democrats may not be entirely certain about their nominee's chances in the state, despite the fact that the last poll there put President Obama ahead of Mitt Romney by 21 percentage points. But it's also simply a response to one of McMahon's greatest advantages: her ability to self-fund. She spent $50 million of her own money on the race in 2010 and has contributed $12.4 million out of her own pockets this time around.

Watch the ad: