Depends on the news outlet. The AP is pretty conservative in its calls, even when they’re early like this, so they typically aren’t the ones to have to retract. That’s more often the news networks like CNN or Fox. Some outlets want the scoop and take more of a risk (calling at 80% likelihood or whatever) while others wait for 90 or 95% so they can present themselves as more reliable. Both are calling what’s likely, but in the former, every now and then you’ll get some races wrong. For the higher percentages it’s much more rare.

It really depends on which precincts are reporting, how big they are, and how it’s comparing to what’s expected. If they remaining half of precincts leans toward the candidate behind, and neither candidate is performing unexpectedly, they would let it play out before calling because they would expect it to tighten up.

That would be the 15% reporting. It’s more about their understanding of which precincts have reported, how much population they represent (urban or rural precincts), and how those precincts would need to break down for one candidate or the other. Then they match it to what report is coming in and make the call if it fits (if Sherman’s strongest precincts were coming in and he was already losing there or underperforming significantly, that’s the kind of red flag they would look for to make an early call)