Whoever wins the Republican primary election for an open Kentucky seat in Congress will then have to face up to the Clooney factor.

Nick Clooney, father of the box-office star George Clooney and a local celebrity in his own right, was unopposed for the Democratic nomination.

The former Cincinnati television anchor and newspaper columnist was recruited to the race for the 4th District by Ken Lucas, the retiring Democratic congressman.

Republican leaders have lined up behind Geoff Davis, a manufacturing consultant who lost a close race to Mr Lucas two years ago.

With help from Hollywood, Mr Clooney has raised over $612,000 (£350,000). Contributors include the Oscar-winning actors Michael Douglas and Renee Zellweger.

Opposing Mr Davis are Kevin Murphy, an attorney, and John Kelly King, a chiropractor running his first race.

Mr Davis has raised $1.1m, more than double the total for Mr Murphy, according to the Federal Election Commission's most recent figures. Mr King has raised $20,000.

The 4th District, which takes in the Cincinnati suburbs of northern Kentucky and stretches to the West Virginia border, has historically tended to vote for a Republican. Mr Lucas, who was elected in 1998, was the first Democratic candidate in 30 years to win the seat.

Mr Clooney opposes abortion and gun control, but Republicans have highlighted his son's liberal views.

"It seems the best way to campaign against my father is to go after me," George Clooney wrote recently in a letter to the Cincinnati Enquirer.