"If I knew technically what a haiku was, it would be a haiku. But I don't think it's technically a haiku," Franken said.
The simple idea captures the two Minnesota Democrats' shared progressive philosophy and explains why they became friends despite differences.
"My dad was always the serious type, so it was interesting how they crafted such a serious friendship," said David Wellstone, the late U.S. senator's son. "But what they connected on was common vision."
Franken probably would not be a senator if not for Wellstone's death in a plane crash with just weeks left in his reelection campaign in 2002. Within a year, Franken began openly discussing a move back to the state where he'd spent most of his childhood to challenge the man who'd won Wellstone's seat, Republican Norm Coleman.
"It might be crazy. I might not be the best candidate," Franken said in a 2003 interview with the Minneapolis Star Tribune.
When he announced his candidacy in 2007, he offered another quote from Wellstone, whom he called his political hero: "The future belongs to those who are passionate and work hard."
Franken stops short of saying he aspires to live up to Wellstone's example. "I can't fill his shoes, so I don't try to," he said. "But he does inspire me."
Franken has made a point of championing some of Wellstone's trademark issues, such as mental health and veterans' issues. One of his proudest achievements, he says, is securing funding for mental health screenings in schools.
He's also taken on issues such as domestic violence that were shared causes of Wellstone and his wife, Sheila. In one floor speech during the debate over reauthorizing the Violence Against Women Act, Franken twice was moved to tears discussing the Wellstones' work on the issue.
"Franni and I have a personal responsibility to carry on the Wellstones' legacy," he said in that speech, referring to his own wife.
"One of the things I like about Al is that he can't talk about Paul without starting to cry," said Amy Klobuchar, Minnesota's senior senator.
One of Franken's favorite stories about Wellstone is of him as a father, tracking his son along the entire length of a cross-country race cheering him onward. Franken uses it in campaign speeches as a way of urging supporters to work hard on his behalf. But it also serves to highlight the two men's differences. "I have a different type of energy," Franken said in typical understatement.
"Wellstone was a cheerleader. He was the drum major. He was the person who would motivate the crowd, motivate people," said Sen. Tom Harkin (D-Iowa), who also considered the senator a close friend and has since forged a bond with Franken. "Al is a little bit different. He goes to work on legislation, sinks his teeth into it and is more of an inside worker perhaps than what Paul Wellstone was."