Lindsey Graham, the late US senator, speaks to reporters on Friday in Kyiv, near destroyed Russian vehicles on display. EFREM LUKATSKY/AP

The sudden and unexpected death of US Senator Lindsey Graham could make things more difficult for Republicans in the Senate, as their thin 53-47 majority is already being strained by the absence of Senator Mitch McConnell.

A temporary replacement for Graham can be named by the governor of South Carolina, though a permanent senator will be elected in November. There was no word on Sunday who might be the temporary stand-in, and candidates to fill the open seat in South Carolina during the midterms are expected to put their names forward this week.

The Associated Press reported on Monday that a number of Republican names began circulating as possible replacements, including Representative Ralph Norman.

Graham was chair of the Senate Budget Committee, which is working through a process to push forward parts of President Donald Trump's voter ID bill. He was also considered a big supporter of the war against Iran, which could be critical as the Senate is due to hear a request for additional funding for that conflict.