However, Trump's Senior Adviser Jason Miller has said it's still "too soon to be calling Arizona".
Republican Senate spokeswoman Natalie Johnson said it as "purely conjecture and insanely irresponsible".
Arizona's Republican Governor Doug Ducey said it was "far too early to call the election".
"In Arizona, we protected election day. Let's count the votes – all the votes – before making declarations," he said.
What this means for the election's outcome
There may be 50 states in America, but when the votes are counted, just a handful of them – Arizona included – decide who wins the presidential election.
In this election, 15 states fall into the category of a "swing state" or "battleground state" – meaning they could conceivably be won by either Donald Trump or Joe Biden.
As for the rest, we already know who will win them: Trump stands no chance whatsoever in Democratic Party strongholds like New York and California, for example, while he's likely unbeatable in heavily Republican territory, like Alabama or Oklahoma.
Worth 11 electoral votes, Arizona has only voted for a Democratic candidate once since 1952 – Bill Clinton, in 1996.
While that may not sound like the voting pattern of a swing state, Arizona was very much in play this election, with Trump only once leading Biden in the state's polling average.
