Andrew Romanoff is challenging an incumbent Democrat for his U.S. Senate seat, officially kicking off his campaign on Wednesday.Romanoff, 43, said the state deserves a lawmaker who is elected, not appointed.He announced his campaign in Pueblo, in front of about 100 supporters. He said he would earn the seat at the polls and wage a harder fight for Democratic ideals than incumbent Sen. Michael Bennet.Without mentioning Bennet by name, Romanoff went straight to the reason Bennet is unpopular with some Democrats: He was chosen by Democratic Gov. Bill Ritter to fill a vacancy and has never before held elected office. "This contest ought to be decided not by a tap on the shoulder but by actual voters -- especially voters who live in Colorado," Romanoff said in an apparent reference to Bennet's sizable fundraising lead of about $2.6 million, mostly from out-of-state contributors. The line drew cheers for the 80 people gathered for the speech.Some Democrats have fretted that Romanoff's campaign will weaken Bennet, who already faces six potential GOP challengers. Romanoff said the primary will energize the party, not hurt its chances next year.Romanoff was previously the Speaker of the House for Colorado, a position he served for four years. Before that he was a Colorado Representative from 2001 until 2009. He left office earlier this year because of term limits.He is currently teaching public policy at the University of Colorado in Denver.Romanoff was considered the front-runner for the senate seat vacated by Ken Salazar when Salazar was appointed Interior Secretary. Romanoff had the endorsement of 62 of 64 Democratic country chairmen during the appointment process when Gov. Bill Ritter appointed Bennet, a relative political unknown.Bennet was the superintendent of Denver Public Schools when he was appointed to fill the final two years of Salazar's term."No one knows the legislative process better, or knows the people of Colorado better," Romanoff told the Pueblo crowd.Bennet was little known outside Denver before his appointment. He has kept up a grueling schedule of statewide meet-and-greets in his first few months in office, but some Democrats remain skeptical of him.Bennet's campaign did not comment on Romanoff's candidacy, other than to say that Bennet is working hard to serve the people of Colorado. Romanoff is the first Democrat to announce he will oppose Bennet.In Romanoff's first campaign speech, he laid out boilerplate Democratic themes -- support for education, clean energy and the working class. He also sought to gain support from Democrats unhappy with Bennet's perceived centrism. Bennet has said many times that he supports a government health insurance option as part of health care reform. But some Democrats gripe he hasn't ruled out any plan that does not have the option. "I don't need to take a poll to take a position," Romanoff said about the issue. "If you spend too much time sitting on fences, all you get are splinters." The approach appealed to Democrats who attended the speech. "I think it's good for the party to have a debate about priorities," said Bruce Boreson of Pueblo, a retired attorney. Boreson said he's unhappy that Bennet has said he would vote for a union-backed bill making it easier to organize. The issue hasn't come before the Senate but there has been lobbying by both sides. "I guess I would just prefer stronger positions," Boreson said. Romanoff planned other speeches in Colorado Springs and Denver on Wednesday.Current Republican candidates for the primary include former Colorado Lt. Gov. Jane Norton, Weld District Attorney Ken Buck and Aurora City Councilman Ryan Frazier.