The ad wars in the race started even before McConnell had an opponent. Pro-Democratic groups already went up with ads earlier this spring against McConnell.
Two weeks ago Senate Majority PAC and Patriot Majority USA announced they were spending $250,000 to go up with TV, radio and digital ads, as well as a new website, to argue that McConnell's been in office too long and that "it's time for a switch."
"Our strategy remains to highlight how after 30 years in Congress, McConnell is out of touch with Kentuckians and he is the symbol of everything that is wrong with Washington," says a source with knowledge of the group's plans. "We plan to continue our campaign using all the tools necessary (paid media, digital media, social media, web presences, etc) between now and the election to hold him accountable."
But the Republican source from Kentucky says that strategy won't work against McConnell.
"He's very different from these other senators who in years past were labeled as too Washington. He goes back to Kentucky every weekend. He knows all the state senators and he knows the party leaders. McConnell is the guy who built Kentucky politics into what it is today."
"There's a reason so many Democrats said no to running against McConnell. He's got universal name ID in the state," added the source.
McConnell's also aired TV commercials. It's extremely rare for an incumbent to go up with spots so early in a campaign cycle, and Grimes charges that McConnell's ads "are based out of fear of losing his 30 year grip on power."
There's a little bit of history that's working in McConnell's favor: Kentucky hasn't sent a Democrat to the U.S. Senate since 1992, when Wendell Ford won re-election.
Next year the Democrats will be defending their slim majority in the Senate. They currently hold a 54-46 edge (including two independents who caucus with the party) over the GOP, which they hope to expand to 55-45 following October's special Senate election in New Jersey. But they will be defending 21 of the 35 seats up for grabs in 2014. Kentucky may be one of the few contests where Democrats hope to go offense.
"The Kentucky Senate race might be the most expensive in the country but that doesn't mean it's the most important. There are at least a half-dozen other Senate races that are more competitive and will decide the majority, but Kentucky will probably make the most headlines," says Nathan Gonzales, political editor at the non-partisan Rothenberg Political Report.
"With the minority leader, a female officeholder, and tens of millions of dollars, the foundation is set for an ugly race in Kentucky," adds Gonzales.