Minnesota Lt. Gov. Tina Smith has been pegged to replace Franken through January 2019. Smith, a Democrat, said she plans to run in the November 2018 special election.
“Tina Smith is the right person at the right time and has my full support both now and when she runs in the 2018 special election,” Ellison said in a statement Wednesday.
Ellison, who became deputy chair of the Democratic National Committee in February, could have mounted a serious challenge to Smith.
Watch: 4 More Special Elections On the Way, So Far
But he appears unwilling to face off against someone whom he called “a progressive champion who will be an extraordinary senator for the people of Minnesota.”
Politicos have murmured about Ellison’s dark horse potential to be the Democratic presidential nominee in 2020, though he has not addressed those rumors.
It is unclear which Republicans in Minnesota will step forward to challenge Smith in 2018. Some Republicans floated the name of former GOP Gov. Tim Pawlenty, who said he remains “politically retired” at the moment.