"Partisan lines" refers to the divisions or differences between people or groups who support different political parties, ideas, or ideologies. Full definition
While the district was made slightly more Republican in the 2001 redistricting process, it's still relatively evenly divided along partisan lines. (voices.washingtonpost.com)
In the past two years, raising the quality of the nation's teaching force has become a priority that cuts across partisan lines. (educationnext.org)
But changing the constitution takes years, and would mean that the non partisan lines would not be in place until 2022, a decade from now. (wxxinews.org)