Because the Demo's never claim to be conservative, nor court conservative votes. If Democrats are running in the race (3-way) than they *ARE* running against the Demo and the republican. Looking at your above response, how can a demo run against a demo.
But what the hey, I'll give you the benefit of the doubt, you are a Libertarian defender, and it may be the bong that is speaking.
Democrat-Republican-Libertarian, three way race both the Demo and the Repub have to run against the Libertarian. BTW I am not a libertarian, I tend to vote conservative or Constitutionalist. Usually one of these parties endorse the Repub so I end up voting that way but I will not be a slave to a party that votes more and more like the democrats every year..