"We're going to win," Joe Biden's deputy campaign manager tweeted shortly before midnight here in the US.

His confidence was repeated minutes later by the Democratic candidate himself, on stage in his home-state of Delaware.

"We feel good about where we are," Joe Biden told the crowd. "I believe we're on track to win this election."

If they're to do it, the three mid-northwestern rust belt states will be crucial: Pennsylvania, Wisconsin and Michigan.

Not to be outdone, Donald Trump took to Twitter in response: "We are up BIG, but they are trying to STEAL the election. We will never let them do it. Votes cannot be cast after the Polls are closed!"

The social media site, so often in conflict with the president recently, immediately flagged it as misleading and then removed it.

Set aside the optimism from both camps and this election is tight, far tighter than many anticipated.

Florida, which would have given Biden an early and almost certain win, declared for Trump as I write this. The Cuban-American Latino vote turned out in big numbers for him.

Democratic "moonshot" states like Texas - which Trump has held- look unlikely to come through. Ohio stayed Republican red - Trump retained his core ground.

Arizona though, if confirmed, is a real coup for the Democratic Party - a firm step forward on the path to power for Joe Biden.

But this uncertainty and jeopardy is the precise scenario that the Biden camp didn't want. They were hoping for a clear win - something decisive that prevented Trump crying foul.

That hasn't happened. Heading into a new day, it's still too close to call.

Pennsylvania could be the key state, as predicted, and we might have to wait a few days for that to conclude.

The legal teams will be ready and primed - the chances of this heading to the courts is high.

Sit tight, it could be a bumpy ride.