They want the former Everton manager to be the right man to take over from Sir Alex Ferguson. They want the success of the last 20 years to continue seamlessly into the next 20.
Some were sceptical when he was appointed in the summer but were prepared to be proven wrong. More than that, they wanted to be proven wrong.
But they are not daft. And most now are coming to the conclusion that something isn't right.
Some reached their tipping point in early December with back-to-back defeats to Everton and Newcastle at Old Trafford. For others it was the consecutive defeats to Tottenham, Swansea and Sunderland in January.
Some reached breaking point in February with the 2-1 defeat at Stoke City. Others were prepared to give him time until they watched the abject performance against Olympiakos in the first leg of the Champions League round of 16.
Even more fans turned after the humiliating defeat to Liverpool. And on Tuesday night came the next stage of Moyes' slow death.
With United 3-0 down to Manchester City, there were the first signs of real dissent from the match-going supporters.
There were isolated incidents of fans calling for Moyes to go as they made their way out of the stadium. It has not turned into full-blown rebellion just yet. But if there's no improvement soon, rebellion can't be far off.
Considering how far United have fallen this season, it is a minor miracle that the supporters haven't yet vented their feelings in a collective outpouring of anger.
Against Liverpool, they sang defiantly for the final 15 minutes, but that wasn't to be confused with support for Moyes. It was simply fans supporting their club on another bad night.
Gradually, more and more supporters are turning. And once that bandwagon starts to roll, it's very difficult to stop.
In a strange way, Moyes has been helped by the fact that the two latest setbacks at Old Trafford came against Liverpool and City. Whatever their true feelings, no United fan wanted to give either club the satisfaction of knowing they were the ones to spark mutiny.
It will be different when Aston Villa visit on Saturday and Bayern Munich arrive on Tuesday.
The match-going supporters are Moyes' last hope. No manager can survive for long without their support. Most have been patient, but the first cracks are beginning to appear.