Waukesha - Incumbent first-term Mayor Larry Nelson and challenger Jeff Scrima will face off in the April 6 general election after the two came out on top of a five-person field Tuesday.Scrima, who owns a real estate development firm and aggressively campaigned against Nelson's emphasis on regional cooperation and the push for tapping Lake Michigan for a clean water supply, pulled in 35% of the vote to Nelson's 26%.Nelson had far-outraised his competitors in campaign donations - nearly $11,000 and most from small contributors, according to finance reports due Feb. 1. His campaign featured several mailings touting progress during his term on issues like replacing the city's radium-tainted water, building a west-Waukesha bypass, benefiting Waukesha through regional cooperation and adding dozens of businesses despite the recession.