Jon Kyl, a Republican former US senator from Arizona who shepherded conservative supreme court justice Brett Kavanaugh through his confirmation hearing, died on Thursday at 84, his family announced.

The cause was complications from a neurological disease, according to a statement. Last December, Kyl announced that he had been diagnosed with dementia.

“We know that Jon belonged to all of Arizona, a state he loved and explored with vigor, curiosity and wonder. Serving his state and nation in Congress was a privilege and responsibility he honored and respected,” his family said.

An attorney, Kyl won election to the US House in 1986 then the Senate in 1994, where he would serve three terms. He rose to become the Republican whip and served from 2007 until departing the chamber at the beginning of 2013, when his party was in the minority.

Kyl lobbied and practiced law after leaving office, but returned to the public eye in 2018 to assist with the confirmation of Kavanaugh, a federal appeals court judge whom Donald Trump had nominated to replace Anthony Kennedy on the supreme court.

As Kavanaugh’s nomination was being considered, Arizona’s Republican governor, Doug Ducey, appointed Kyl to fill the seat left vacant by the senator John McCain’s death. Kyl served in the chamber for the final three months of the year and voted to confirm Kavanaugh, before resigning and being replaced by Republican Martha McSally.

Katie Hobbs, Arizona’s Democratic governor, called Kyl “a dedicated statesman who always cared deeply for our state”.

John Thune, the Republican Senate majority leader, said Kyl “loved his state of Arizona and was a true legislator’s legislator”.

Thune added: “He was an incredibly hard worker and honorably returned to service when his state called. He was a dear friend and will be missed.”