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.

While Tuesday's special election in Arizona may not seem like the type of story to generate nationwide headlines, the race is getting eyes across the country for boiling down the current state of the Democratic Party into a single election.

The race to fill Raúl Grijalva's seat is expected to be a three-way contest, with the former congressman's daughter in the slight lead.