The politics in Boulder are actually far from as clear-cut as I once thought. As an open minded, college-town environment, there are actually quite a few new urbanist type thinkers in town - and the development community and landowners are practically foaming at the mouth to build more density in many places. But, as in most places, the YIMBY's rarely show up to public meetings or speak their minds passionately on the issue. The opposition, on the other hand, lead by the group PLAN Boulder
is extremely vocal and has essentially controlled planning policy in Boulder dating back to the greenbelt of the 70s (back when that was actually an extremely progressive idea).
Control of council, as best as I can tell, sorta goes back and forth between people of differing mindsets. The area of town around the 29th street mall (officially called the "Boulder Valley Regional Center") and the Boulder Junction area are actually zoned for higher densities than downtown Boulder in the long term. These area land use plans and zoning codes were pushed through by previous councils at points in time when more of the pro-density people were around. Boulder Junction, in particular, was a major loss for the PLAN Boulder folks, and now that they see it getting built they are PISSED. They would like to stop it retroactively, but council is pretty clear at the moment that they aren't going to revisit that area, as the area plan is less than 10 years old and was passed with plenty
of public process.
I can't entirely tell what the current balance is, they have good poker faces, but they seem to be fairly reasonable as a whole at the time being (an all-out moratorium on development was loudly shot down by most of the council last fall, and the council member who brought it up chastised for the message it would send the business community).