A hotly contested presidential election in Arizona has led different scorekeepers to draw different conclusions about the winner of its 11 electoral votes, with some news organizations, led by the Associated Press, calling it early for Democrat Joe Biden even as others maintain the state is too close to call.

The AP is standing by its Arizona decision as the race has narrowed to a difference of 68,390 votes or 2.3 points. And President Donald Trump's campaign has demanded that the race call be rescinded.

The Arizona decision is crucial because with that state's 11 Electoral College votes, Biden is at 264 Electoral College votes and needs just one more state to surpass the 270 he needs to claim victory.

Fox News has also called Arizona for Biden, but other networks, including CNN, have not. Those news organizations make their own judgments, based on data from the Associated Press and other sources.

With its long experience in race calls and sophisticated system of gathering election returns, the Associated Press is the nation's semi-official arbiter of election night wins. The official results are certified by states — often weeks after the election — before the Electoral College decides the presidency in December.

Many news organizations, including Bloomberg News, follow the Associated Press. Bloomberg will also consider a race to be won if two or more major networks make an independent race call.

AP called Arizona for Biden at 2:50 a.m. Wednesday. At the time, about 80% of the anticipated vote had been counted, and Biden was ahead by 130,000 votes — about 5 percentage points.

As of late Wednesday, there were 480,000 votes left to be counted. Trump would need to win 58% of them — and most of the votes are in Maricopa County, which includes Phoenix, and which Biden is winning by 4 percentage points, according to the Arizona Republic.

The AP continues to monitor states even after they've been called and will take those electoral votes off of its tally if new results indicate that the original call is in doubt. The AP has not indicated it intends to do so this time.

Fox and the AP use a combination of election returns, voter surveys, turnout models and other data to make their race calls. Both organizations use the same survey operation, called VoteCast, to help make those judgments.

Part of the confusion about Arizona came from an error from a traditional exit pollster, Edison Research, which over-estimated the percentage of votes counted in Arizona. Edison corrected the error, but the Associated Press does not use Edison data and made its race call independently.

"I know everyone is on a hair-trigger looking for conspiracies and manipulations of the data but that was just a programming bug that took us a few minutes to fix Wednesday morning," Edison President Joe Lenski said.

Arizona was a turning point in the election night narrative, providing Biden with his first chance to flip a a state that Trump won in 2016. But Arizona also had deep symbolic value: It's a state that has voted Republican in every election since 1996 and is home to GOP presidential candidates Barry Goldwater and John McCain.

Arizona has a 28-year track record with mail-in voting, and was able to process those ballots before polls closed on Tuesday night.