Question

how does partisanship help the political parties

Answer 1

what is partisanship

Answer 2

If something is prejudicial towards a particular point of view, you can call itpartisan. You'll often hear of thepartisan politics in the U.S.— since politicians seem to be completely devoted to the agendas of their own parties.

Partisan can be used to describe rabid supporters of any person or activity. In American English, however, it is most often used to refer to politics and the American two-party system of Democrats and Republicans. A bill introduced may have partisan support from the party that introduced the bill, or — more rarely it seems to American voters — the bill may even have bipartisan support. The prefix bi is added to show the support from both parties.