Capito has already raised close to $3 million for her Senate race, according to federal campaign finance records. Callaghan said Tuesday a race against Capito would be a challenge.
"It's a difficult race to run," Callaghan said. "Shelley Moore Capito is a formidable candidate."
That previous campaign experience would be a benefit in a potential Senate race, Callaghan said. It's not the same as a statewide race, but he said he thinks it could have laid the groundwork for such a campaign.
West Virginians are better off if Democrats control the Senate, Callaghan said. He said "like everybody else" he has criticisms and concerns with some of the policies of President Barack Obama and his administration.
But the state's interests are still in better hands with Democrats, he said.
Recently, Sen. President Harry Reid, D-Nev., has been outspoken in his confidence that a West Virginia Democrat would soon announce his or her candidacy. Callaghan said he spoke with Washington officials but wouldn't give any names.
He has apparently not spoken with current state Democratic Party Chairman Larry Puccio. In a phone interview Tuesday, Puccio said he wasn't aware Callaghan was still interested.
"I did not know that. I know Mike, and Mike is a fine gentleman," Puccio said.
He added Callaghan is extremely intelligent and always looking to be involved.
Puccio said he still can't say whether Tennant will run. He knows she's very interested and hopes she runs, but doesn't know of any imminent announcement.
There's plenty of time to mount a senatorial campaign, Puccio said. He wouldn't be surprised if more than one person still decides to toss his or her hat in the ring.