Acting Attorney General Todd Blanche cleared a critical hurdle Tuesday in his bid to be confirmed to the post.
A special election will be held in the coming months, according to state law.
NATO allies, Ukraine and Israel have paid tribute to U.S. Sen. Lindsey Graham as a friend and advocate of trans-Atlantic ties.
Lindsey Graham, a longtime Republican senator from South Carolina, died on Saturday after a "brief and unexpected illness," his office said. He was 71.
Graham Platner officially withdrew from the Maine Senate race on Friday.
Maine Democratic Senate candidate Graham Platner announced in a video posted on social media Wednesday that he is suspending his campaign.