Congressional elections live updates: Senate and House control could be decided by a handful of races

This election's biggest prize is undoubtedly the presidency, but the results of dozens of other downballot races will also have a lasting influence over what happens in the U.S. federal government for the next several years.

Whoever wins the presidency will have to work with Congress to implement their agenda, and that becomes much easier if one party captures the White House and both chambers on Capitol Hill. But if the parties split Washington's power centers, it will likely force a season of compromise, as well as provide a significant check on the president's agenda.

The Associated Press has been tallying results in national, state and local elections since 1848. In broad terms, the process is the same today as it was then: Vote count reporters collect election results at a local level as soon as polls close, then submit those results for the AP to collate, verify and report.

This year, AP will count the votes in about 5,000 contested races around the United States, from the presidency and Congress to state legislatures and ballot measures.

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 plays a role in collecting and standardizing the results.