Three scenarios for how the US midterm results could unfold

This scenario involves Republicans resiliently holding on to both chambers of Congress.

For this to happen, the polls - which have previously underestimated Trump's support - need to be wrong and the toss-up races to mostly fall the way of Republicans.

Not only would Republican voters have to turn out in unexpectedly impressive numbers, independent and Hispanic voters who had seemingly soured on Trump's policies would have also to break his way in the end.

In this scenario, control of the House, far from being a done deal for Democrats, could end up coming down to California and its extended days-long counting process for mail-in ballots.