The fact is that the explicit threat doesn't need to be made for there to be a threat - the Tea Party generally did not make explicit threats. The implicit threat by demonstrating a significant portion of the voting base as adhering to your ideas is, itself, a threat.
Meanwhile, progressives very often, as demonstrated on here, regularly say "The Dems haven't done what we want, don't vote Democrat!" and act surprised that their total lack of demonstration of support in elections for progressive candidates has failed to give them pull with the national party with this threat.