Since the Republicans in 2010 got about 44 million votes and in 2014 got over 45 million, I'd say that means a turnout of over 46 million votes. I think elsewhere he's clarified that he's not predicting that the Republicans would still control the House, just the votes would be up. His rationale is IMHO fuzzy: Republicans love the feeling of the victory of 2016 (Adams was an early and sole predictor of Trump's election), they tend to act more than talk and are bashful in talking to pollsters so the current polls underestimate GOP turnout (it's an echo of an early 21st century meme that voters who opposed black candidates would not admit that to pollsters).'Dilbert' cartoonist predicts huge GOP midterm turnout https://t.co/H1htybgZjj— Scott Adams (@ScottAdamsSays) October 30, 2018
My record on predictions is bad, so I won't officially predict that Democratic turnout will top the Republicans and top 47 million votes. We'll see.