Because Denver has a single city and county government, and a single school board for the entire 550,000 or so people within its boundaries (more the entire population of Wyoming), it has a relative shortage of minor political offices. Moreover, many of those, from the Mayor, to the District Attorney, to the Election Commission, to a couple of seats each on the City Council and School Board, are at large positions, which require candidates to run a huge well organized campaign in order to reach so many people. Such races are a hard way to get started in politics. Running for city council or the school board in Denver requires five figure plus campaign budgets, an organized staff, and media savy.
But, Denver does have its own minor leagues of politics in the form of "RNOs" (registered neighborhood associations), whihc provide input to developers, traffic project managers and the city on new developments. There are more than 50 in the city, and they provided an entre into politics for both Andrew Romanoff, who is now the Speaker of the House in the state legislature, and Kathleen McKenzie, who is now on Denver's city council.
Thanks again to the Washington Park Profile for the tip.