Republican US senator Lindsey Graham has said the Democrats’ treatment of Supreme Court nominee Brett Kavanaugh is the “most despicable thing” he has seen in politics.

Mr Graham said that Democrats sat on allegations against Mr Kavanaugh and then sprung them on the nominee at the last minute in a desperate attempt to prevent his confirmation.

Supreme Court Kavanaugh
Supreme Court nominee Brett Kavanaugh gives evidence (Win McNamee/AP)

The South Carolina senator said Democrats want to “destroy” Mr Kavanaugh’s life and hold the seat open in the hope of winning the White House in 2020.

Mr Graham said a vote against Mr Kavanaugh would “legitimise the most despicable thing I have ever seen in politics”.

He also called the Democrats’ tactics “the most unethical sham”.

Mr Graham supported Republicans’ ultimately successful efforts to block action on President Barack Obama’s Supreme Court nomination of Judge Merrick Garland.

The Supreme Court gives binding rulings on subjects such as abortion and same-sex marriage and recent nominations for the panel have been conducted on fiercely partisan lines.

President Donald Trump has already successfully nominated Neil Gorsuch for the vacancy created by the death of Antonin Scalia with his predecessor Mr Obama unable to install his choice.

Mr Trump’s nomination of conservative Mr Kavanaugh to replace the retiring Anthony Kennedy is yet to be approved.

White House press secretary Sarah Sanders tweeted in support of Mr Graham’s intervention.

Ms Sanders tweeted: “.@LindseyGrahamSC has more decency and courage than every Democrat member of the committee combined. God bless him.”