We're going through withdrawal. Memories of once-regular characters like Fred Thompson, Chris Dodd, and the slew of other presidential contenders are beginning to fade. And though Hillary Clinton and Joe Biden have stayed in the picture — benefiting from President-Elect Obama’s “Team of Rivals” approach — what about the remaining cast of challengers we grew to know (and occasionally love) over the past two years?

Fans of Fred Thompson can look forward to a small-screen return for the politician-turned-actor-turned-politician (though no official word yet on whether he will reprise his role on NBC’s Law & Order.)

Mitt Romney has kept his name in the public arena. Though John McCain passed him over for VP, he continues to opine on economics and politics, including a guest op-ed in The New York Times last week with the candid message, “Let Detroit Go Bankrupt.”

Then there’s the busy bee of the one-time Republican hopefuls: Mike Huckabee. Since exiting the race, he formed Huck PAC, a political action committee that supports, “Republican candidates who are passionate advocates for tax reform, a strong national defense, real border security, life, the family, less government, and individual liberty.” Huck has also written a book titled, Do the Right Thing: Inside the Movement That’s Bringing Common Sense Back to America, which he’s currently hawking on a book tour, and he hosts a television show on Fox News Channel called, excitingly, Huckabee. Set your DVRs for weekends at 8 p.m.

Meanwhile, over in the Dem’s camp, remember the champion of impoverished America, the guy who charmed us with his flashy smile and stunning head of hair? Yes, John Edwards returned to the spotlight for the first time since coming clean about his affair with a campaign staffer. Edwards appeared at Indiana University to speak about politics and poverty, but made no mention of his personal life.

As for the others, some, like Chris Dodd and Dennis Kucinich, returned to their previous posts. Bill Richardson is slated to follow in Clinton and Biden’s footsteps, taking an Obama cabinet spot as Commerce secretary.

Don’t miss ‘em too much… Many will be back on the campaign trail before you know it. Rudy Giuliani, for instance, is already hinting at the possibility of a run for governor of New York in 2010.