Romney, who lost to President Barack Obama in 2012, became one of the sharpest Republican critics of then-candidate Donald Trump during the 2016 election campaign, and some hope he will continue to be a voice of opposition within the Republican party.
"Here's what I know. Donald Trump is a phony, a fraud. His promises are as good as a degree from Trump University."
Romney is considered likely to win the Senate seat. He's well known and respected in Utah, where he successfully managed the 2002 Salt Lake City Olympics. He is a leading member of the Latter Day Saints church, commonly known as the Mormons, whose members are a solid majority in heavily Republican Utah.
Al Jazeera's Rob Reynolds reports.
