Grover Norquist and the Tea Party had had an effect on the political scene with a relatively small number of people involved. Their technique is simple power politics---work like hell to defeat anyone who disagrees with them. If a populist movement has any significant support, they can do the same: Agree to work to defeat any candidate who votes "wrong" on a particular issue, regardless of party. One such issue could be raising high-income tax rates.
    Powe in politics is most effectively used in threatening to defeat "bad" candiates, rather than trying to create "good" ones.