In a speech at the Nashua Community College in New Hampshire, Clinton told stories about the early days of their relationship.
"I thought she was the most amazing person," he said, describing the two meeting and falling in love nearly 45 years ago.
"Everything she touched, she made better," he said.
Clinton was less charitable toward the Republican presidential candidates. Though he didn't mention anyone by name, he said the entire field is "kind of scary."
Clinton's speech marked the beginning of what is expected to be a month-long drive to help his wife win the Iowa caucuses and New Hampshire primary. Though Hillary Clinton officially entered the presidential race in April 2015, her husband hasn't yet had a speaking role. Instead, he has mostly offered advice and helped fundraise behind the scenes. His decision to return to the campaign trail in New Hampshire is notable because that's the state that boosted his own campaign in 1992. Heading into the 2016 primary, Hillary Clinton is fending off a challenge from Sen. Bernie Sanders, who represents neighboring Vermont.
Bill Clinton joked that he is out of place on the campaign trail in the current political climate.
"I don't fit anymore," he said. "First of all, I'm a happy grandfather. I'm not mad at anybody."
The former president, who President Barack Obama has dubbed the explainer-in-chief, was a controversial figure in Hillary Clinton's 2008 campaign -- when exit polls showed
that particularly in states like South Carolina, his negative attacks on then-Sen. Obama could have had a net negative effect.
In this campaign, Bill Clinton said, Hillary Clinton is pursuing "politics that are inclusive enough to actually get something done."
"I think this election is about restoring broadly shared prosperity, rebuilding the middle class," Clinton said.
He said his wife once excitedly came home explaining how she'd found a human side of Tom DeLay, the former House Republican leader and nemesis of Democrats whom she'd discovered was also an adoptive parent.
Monday's nearly 30-minute speech came in front of an audience of about 720 people in the community college's gym, according to Nashua's fire marshal.
Clinton's arrival is not a guaranteed success, and Republicans -- including Chris Christie
who was also in New Hampshire Monday -- attacked Clinton as "going backward."
And GOP front-runner Donald Trump has recently revived Clinton's past scandals -- including Monica Lewinsky
-- as a way to attack the Clintons.