Left-wing candidates backed by Mayor Zohran Mamdani won multiple House primaries on Tuesday, defeating establishment-endorsed Democrats including sitting Representatives Espaillat and Goldman in New York. The wins represent a real shift in Democratic primary dynamics, though they're concentrated geographically and the term 'tidal wave' overstates the scale — only a handful of races flipped to the left, not a party-wide movement. Democratic Socialists are simultaneously organizing to influence the 2028 presidential race, suggesting they're building a longer-term challenge to centrist leadership. This is one cycle's worth of gains in a fractious party, not a wholesale takeover.