A senior Republican lawmaker's son has donated the maximum legal limit to the Democratic challenger running in an election to replace his father.

Virginia congressman Bob Goodlatte is not seeking re-election in November.

On Sunday, his son Bobby Goodlatte said he gave $2,700 (2,100) to Jennifer Lewis, a Democrat who is running in Virginia's 6th Congressional district.

"2018 is the year to flip districts - let's do this!" he said, linking to Ms Lewis' website.

Jennifer Lewis, 26, is a mental health care worker running to replace Mr Goodlatte in the central west part of the state.

She supports liberal policies such as legal cannabis and a $15 per hour minimum wage, and will face Republican state delegate Ben Cline in November.

The Lewis campaign told CBS News in a statement on Monday: "We appreciate Bobby's generous donation, and we're thrilled to work alongside a Goodlatte from now until November to flip the district blue."

The maximum donation permitted by an individual is $2,700.

Mr Goodlatte, 65, serves as the powerful chairman of House Judiciary Committee, and is the most senior Republican in the state's congressional delegation.

Last November, after Virginia elected a Democrat as governor, he announced that he would not seek re-election after 13 consecutive terms.

He joined more than a dozen Republicans who have announced that they are not seeking re-election in 2018.

According to his Twitter account, his son Bobby is an investor based in San Francisco.

In a subsequent tweet, Mr Goodlatte Jr said he was "overwhelmed with the support", but told followers "don't just retweet - donate!!".

Later on Monday, Mr Goodlatte Jr tweeted about the firing of FBI agent Peter Strzok, who came under scrutiny for texts criticising President Donald Trump during the 2016 election.

He blamed his father, who took aim at Mr Strzok during a House hearing last month, for ruining the FBI agent's career.