After the release of census data, political bodies such as state legislatures, county commissions, city councils and school boards begin the process of redistricting. Usually, each political body redistricts itself. For example, the state legislature is generally responsible for redrawing the lines for congressional districts as well as state house and state senate districts. Likewise, local governments at the county and city level redraw their own district lines. In certain instances, redistricting is not left to the incumbent politicians, but rather is performed by one or more redistricting commissions. Each state has its own deadlines governing when redistricting must be completed.