Progress Kentucky's other candidates include, among others, Reps. John YarmuthJohn Allen YarmuthDem lawmaker: Trump finally got his 'largest audience ever' in London protests Dems struggle with unity amid leadership tensions Overnight Health Care: Pfizer delaying price hikes after Trump criticism | Dems focus on health care in Supreme Court fight | Feds won’t reunite all 102 detained children by deadline | VA nominee headed to Senate floor vote MORE (D-Ky.) and Thomas Massie (R-Ky.), the latter of whom is backed by the Tea Party; Kentucky Secretary of State Alison Lundergan-Grimes (D); and former gubernatorial candidate Phil Moffett, also a Tea Party candidate.

In a statement accompanying the petitions, Shawn Reilly, executive director of Progress Kentucky, echoes what a number of Democrats in the state believe: "It’s unacceptable that someone as unpopular as McConnell would be unopposed for a sixth term."

McConnell was revealed to be the nation's least popular senator in a poll released last month by Democratic firm Public Policy Polling, and though he led a number of Democratic challengers, Judd took 43 percent support to his 47, indicating he might be vulnerable.

Polls released prior to that one, however, indicated the senator is much safer, and he has won four of his five elections with more than 50 percent of the vote and has nearly $7 million in his war chest, a considerable sum for any challenger to surmount.