"Few people think the parliamentary arithmetic will change very much"
Wait, what? Am I taking crazy pills? All the current data suggests that there will be a big change, doesn't it? Of course, polls aren't entirely reliable, a week is a long time in politics, and things can change. But every single recent poll has predicted a resounding Tory victory.
The last 4 polls have placed the Tories 12%, 6%, 10% and 14% ahead. The problem is that Brexit Party voters are heading back to them, while the Remain voters are steadfastly split between Lib Dems, Greens and Labour. In terms of the electoral calculus, 6pts is generally the critical figure for a skin-of-your-teeth majority.