GOOD THUNDER, Minn. - One number is never far from Sen. Al Franken's mind: 312.

That was his official margin of victory six years ago in the Minnesota Senate race. The extremely narrow outcome of his first campaign, he said, influenced his comedian-to-senator transition to office and is at the heart of his quest to win a second term in November.

"I felt that I wanted to prove to all Minnesotans that I was going to work for them," Franken told "This Week" on Sunday. After five years in office, he still begins many sentences with the phrase, "When you win by 312 votes."

During his first term, Franken has been purposefully selective when using humor. But he bristles at the suggestion that he's only become serious since arriving in Washington.

"I was always a serious person," Franken said. "I don't think there is a conflict between being funny and being serious. I think people who are funny are often very serious people and vice versa."

Two decades after headlining the White House Correspondents' Association dinner, where he poked fun at First Lady Hillary Clinton's health care plan, Franken is back home in Minnesota this weekend. He sat down with "This Week" during a tour of rural Minnesota, his first Sunday interview since he was elected to the Senate,

He may still have the most famous laugh in politics, but these days Franken is delivering a different kind of punch line. He laughed when asked about comedian Al Franken would say about Senator Franken's first term.

"He would say I did well because I'm the same person, not two different people," Franken said, adding that he would be "a really hard person to satirize" because "I've just been impeccable."

With a chuckle, he said: "I've made some small mistakes, I suppose."

While Franken didn't arrive in the Senate until six months after the rest of his freshman class, after a recount with his Republican rival Norm Coleman delayed his swearing in, he is not among the most endangered Democrats up for re-election this fall. One Republican Senator told ABC News that Franken had been a "surprise," for having a "serious and studious" first term.

Four Republicans are fighting for the chance to challenge Franken. The state's Republican primary is set for August.

Franken acknowledged that some of his fellow Democratic senators were worried about their re-election bids, but when asked if it was difficult to run as a Democrat during President Obama's sixth year, he said: "I'm very comfortable doing that."

While he criticized the rollout of the health care law as "pretty disastrous," Franken also said Democrats should not be afraid to campaign on the benefits of the Affordable Care Act. He said parts of the law still need to be fixed legislatively.

Franken has become a fierce critic of big corporate mergers and the loudest opponent in Congress to Comcast's bid to take over Time Warner Cable, arguing it's a losing proposition for consumers.

In an effort to learn about the state - and strengthen his appeal to rural Minnesota voters - Franken has harvested corn with Kevin Paap, president of the state's Farm Bureau. Members of the group endorsed Coleman in 2008.

"Senator Franken was on my farm two years ago and combined five acres for me," Paap told ABC News. "He had never been in a combine, he asked to learn more about combining corn, biotechnology and he spent a day on our farm. He certainly has that attitude that I want to learn more, I want to know how to help."

Franken, who has traded a television audience of millions for far smaller crowds of voters, said he didn't miss his time as a comedian.

"I really enjoyed my other career," Franken said. "But this is a great job. This is a great job."

He added: "But it's also great to make people laugh."

If he wins re-election in November, he'll have the last laugh, completing his transition from comedian to senator.

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