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.

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.

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.