Attorneys for Ohio Republican officials will call witnesses this week to defend the state's congressional map.

A federal trial enters its second week Monday in a lawsuit by voter rights groups that say the current seats resulted from "an unconstitutional partisan gerrymander." Their witnesses have included Democratic activists and voters who have expressed frustration and confusion with districts that have stayed at 12 Republicans, four Democrats, since they were drawn ahead of the 2012 elections.

Attorneys for the Republican officials being sued say the map resulted from bipartisan compromise, with each party losing one seat after population shifts in the 2010 U.S. Census caused Ohio to lose two congressional seats.

Among potential GOP witnesses is former U.S. House Speaker John Boehner (BAY'-nur) of West Chester, Ohio.