Once upon a time, PD was a powerful force on the city and county level. The party came very close to holding outright majorities on the Common Council and had a presence that demanded co-operation from liberal/moderate Democrats on the County Board.
Today the picture is quite different. Progressive Dane has four endorsed members of the County Board and three on the City Council. Of the three on the Council, only one, Marsha Rummel, does not also affiliate with the Democratic Party in some capacity. The Council PD caucus still meets regularly, and includes former Ald. Brenda Konkel, but from what I've heard, the County caucus rarely meets and strategizes anymore. That's not to say it doesn't have powerful members but they're simply not large enough to think as a party anymore.
What are the political dynamics that shaped PD's decline in stature? What did the 1990's offer to left wing local movements that the past few years have lacked? I can only guess.
The Democratic Party is at least partially to blame. In the early to mid-2000's, the Dems actively worked against candidates with PD affiliations even those with very loose ones. Groups like AFSCME rather bluntly discriminated against candidates with PD staffers or PD endorsements, in favor of candidates whose loyalty they could count on. From what I've heard, 2007 was the last year in which a major showdown between the two groups occurred.
However, in some cases, former PD activists got upset with PD's effectiveness and obsession with pet issues, including some that weren't entirely relevant locally, such as international advocacy (Israel-Palestine etc.).
And although most people who vote in local elections do distinguish between the local and the national, the former inevitably is affected by the latter. For instance, in a national context, some progressives were upset with the compromise that Bill Clinton represented for the major left-leaning U.S. party. An example would be Ben Manski, who saw Clinton's nomination in 1992 as too much to bear.
Conversely, the era of W. and the increasingly extreme rightward tilt of the GOP may have influenced some on the left to abandon their idealism and compromise yet again in favor of Democrats during the last decade. At least one former PD member has told me he left the party when it endorsed Nader in 2000.