And bear in mind that climate change is by far the most important issue facing America and the world, even if the people selecting questions for the presidential debates for some reason refuse to bring it up. Quite simply, if Democrats take the Senate, we might take the minimum action needed to avoid catastrophe; if they don’t, we won’t.

What about the House? All, and I mean all, of the Obama administration’s legislative achievements took place during the two-year period when Democrats controlled both houses of Congress. Can that happen again?

Until the last few days, the chances of flipping the House seemed low, even if, as now seems all but certain, Democratic candidates in total receive more votes than Republicans. Partly that’s because G.O.P.-controlled state governments have engaged in pervasive gerrymandering; partly it’s because minority voters, who overwhelmingly favor Democrats, are clustered in a relatively small number of urban districts.

But a sufficiently big Clinton victory could change that, especially if suburban women desert a G.O.P. that has turned into the gropers-owned party. And that would let her pursue a much more expansive agenda.

There’s not much mystery about what that agenda would be. I don’t know why so many pundits claim that Mrs. Clinton lacks a vision for America, when she has actually provided an unusual level of detail on her website and in speeches.

Broadly speaking, she would significantly strengthen the social safety net, especially for the very poor and children, with an emphasis on family-related issues like parental leave. Such programs would cost money, although not as much as critics claim; she proposes, credibly, to raise that money with higher taxes on top incomes, so that the overall effect would be to reduce inequality.