2016 brought a lot of change in presidential primaries, but mostly continuity in House and Senate primaries. How will the candidates gain party support and win votes in this year's crowded primary season? Hans Hassell says party elites and donors continue to decide the vast majority of primaries by clearing the field and providing support. Robert Boatright says the story of primaries as ideological battles contributing to polarization is way oversold. Neither sees 2018 breaking the historical mold.