For more than two decades, much of Southern Arizona was represented by Rep. Raúl M. Grijalva, a liberal stalwart who championed environmental causes, supported immigrant rights and advocated on behalf of indigenous communities.

An Arizona special election primary Tuesday to replace the late Rep. Raúl Grijalva is the latest flare-up of the Democratic Party’s clashes over age and experience.

Tensions within the Democratic Party over age, representation and experience have roiled a special election primary in southwest Arizona, where a young, social media-savvy activist is taking on the daughter of Rep.