During reconstruction, a was a southern white who joined the republican party.

The correct answer is:

Scalawags.

Scalawags were white Southerners who defended Reconstruction and the Republican Party, following the American Civil War.

Like the related term carpetbagger, the term has a long history of use as a slur in Southern discussions.

This word is usually applied in historical studies as a neutral descriptor of Southern white Republicans, but some historians have dismissed the term because of its history of pejorative connotations.

use wikipedia, i think they have this.