It's election season again. This is why and how AP calls races across the country

The Associated Press has compiled votes and declared winners in elections across the nation for nearly 180 years. The U.S. doesn’t have a nationwide body that collects and releases election results. Elections are administered locally, by thousands of offices, following standards set by the states. In many cases, the states themselves don’t even offer up-to-date tracking of election results. The AP fills this gap by compiling vote results and declaring winners in elections — providing critical information in the period between Election Day and the official certification of results, which typically takes weeks.