Update: 5:43 p.m.
The Democratic Party has filed a complaint with the Senate ethics committee.
Democrats claim that soon after Mitch McConnell had breakfast with a top airline executive in the Senate Dining Room, the executive contributed to McConnell's campaign.
McConnell campaign spokeswoman Allison Moore says the Democratic complaint is a frivolous attempt to divert attention from Grimes' problems.
The Republican Party of Kentucky has submitted a complaint to the Federal Election Commission alleging Democratic U.S. Senate candidate Alison Lundergan Grimes accepted prohibited campaign donations from her father's company.
The complaint was hand delivered to the FEC Friday morning. It alleges Signature Special Event Services, owned by Grimes' father Jerry Lundergan, purchased a touring bus and then leased it to Grimes campaign at below market rates. Federal law bars companies from giving gifts to campaigns.
A spokeswoman for the Grimes campaign called the complaint a political stunt and said their compliance experts have done their due diligence and stand by the rental agreement the campaign made.
The FEC dismissed a similar complaint in 2010 involving a campaign bus rented to Nevada Republican Senate candidate Sue Lowden by a campaign donor.