It certainly raises speculation by folks about his future, but he remains in a position at this time that he does not intend to run but doesn't rule it out.

Harkin's good with organized labor, teachers, seniors and environmentalists. And when he endorses, he doesn't just endorse, he actively works for you.

Many will speculate that this signifies that Tom is thinking about running for president, when in fact, that is not what this invitation is all about.