Zerban vowed a "long, hard fight," however, and said his message that it's time for a change would strike a chord with voters of the 1st Congressional district.
The Democrat from Kenosha spoke to about 135 enthusiastic supporters at the UAW Hall on Monday night.
"This is not going to be an easy fight. He has a lot of money," Zerban said of seven-term Republican Paul Ryan of Janesville.
Zerban did not mention the fact that he was speaking in Ryan's hometown.
Zerban campaign manager Lisa Tanner told the crowd that the campaign would use every social media outlet available as well as traditional ways of reaching out.
But in the end, the most effective way to win votes is personal contact among friends and family, Tanner said.
Tanner also announced the formation of "issues committees" to advise the candidate.
Tanner boasted of previous work in Kentucky, where she said she was a field organizer for Democrats who won their races, something Democrats don't often do in that conservative state.