But his entry didn't persuade other Democrats to drop their own plans.
Hammond Mayor Tom McDermott Jr. said Friday he will join the race. Former Secretary of State Joe Hogsett said he's keeping his options open. And the wait continues to learn whether U.S. Rep. Baron Hill will join the fray.
Charlie Cook, who handicaps political races for his Washington-based Cook Political Report, already has switched the Senate race to "leans Republican."
And with Ellsworth's jump to the Senate race, Cook switched the 8th District from "likely Democrat" to "leans Republican."
Without incumbent Ellsworth on the ballot, he said, Democratic chances in a year when Republicans are on the rise are slim.