The Progressive Change Campaign Committee's second ad in the campaign features, similar to the first, a Kentucky gun owner who expresses disappointment with McConnell's stance on expanding gun control measures.

"I only shot my rifle one time this last season. One Shot, one deer. But I'd be a pretty bad hunter if I needed an assault rifle to shoot that buck," says Gary Nutt of Cub Run, Ky., in the ad.

"The NRA and the gun manufacturers have given a ton of money to Senator Mitch McConnellAddison (Mitch) Mitchell McConnellGOP moves to cut debate time for Trump nominees McConnell hits back at 'ridiculous' Chinaperson remark GOP senator: 'We were there' on immigration before talks got derailed MORE. And now he's blocking reform. Senator, whose side are you on?" Nutt asks at the end of the ad.

It is backed by a $25,000 buy and will air for a week, starting Monday, on broadcast and cable networks in various Kentucky markets, including Lexington and Louisville, and in Washington, D.C.

PCCC is also airing the ad online, and will expand the buy as it brings in donations to do so via online fundraising, as it did with its first ad.

Including this buy, PCCC has now spent $100,000 on attacks in an early start to what's expected to be one of the nation's most hotly contested races in 2014.

Though McConnell has the advantage of incumbency and a more than $7 million war chest that's expected to grow into eight figures by the time Election Day rolls around, Democrats and Tea Party Republicans both believe he's vulnerable.

One prominent potential Democratic opponent, actress Ashley Judd, recently met with local donors in Kentucky and strategists with the Democratic Senatorial Campaign Committee in Washington about launching a bid for Senate — signs that she's moving closer to a campaign.

And Matt Bevin, a Kentucky businessman who owns a bell manufacturing company in Connecticut, has expressed interest in challenging McConnell in a primary and has reached out to some Tea Party groups in Kentucky.

Watch the ad: