MADISON — It was a surprisingly upbeat Russ Feingold who late Tuesday conceded the loss of the U.S. Senate seat he held for 18 years to Republican Ron Johnson.

Quoting folk singer Bob Dylan, Feingold declared his heart is “not weary — it’s light and free.”

What he said next during his short concession speech left the crowd wondering whether they soon could see the Democratic senator back on the campaign trail.

“I hope and I intend to continue to work with all of you in the future as much as possible,” Feingold told about 300 supporters at the Madison Marriott West. “So it’s on to the next fight. It’s on to the next battle. It’s on to 2012. And it is on to our next adventure — forward!”

The speech fueled speculation Feingold might run for president against Barack Obama or seek the seat of fellow Democrat Sen. Herb Kohl in 2012. Democratic Party of Wisconsin Chairman Mike Tate pooh-poohed both scenarios.

“He’s not going to run for president. He’s not going to challenge Herb Kohl. I believe Herb Kohl is going to run for re-election,” Tate said, adding, “the Democratic Party is very excited about that.”