On what issues are Democrats taking such risks?

(1) Their undisguised faith that Donald Trump and his campaign colluded with Vladimir Putin’s Russia to steal the 2016 election. Maybe I’m wrong, but I don’t think this happened or that it has or will come anywhere close to being proven.

(2) The Republican tax bill was a “scam” that was going to take money away from those with modest incomes. A look at the tax rate schedules in the Republicans’ bill should have told Democrats that this argument wasn’t sustainable, and perhaps they made it in the hope—which didn’t seem too far-fetched at the time—that enough Republicans would waver, the bill would never pass and their characterization, with predictable help from the mainstream media, would stick. But the bill passed, modest and low-income people are getting raises and bonuses, and just about everyone will get a bigger paycheck later this month.

(3) Their claims that the Republicans were responsible for shutting the government down last month over DACA. Democrats knew that DACA was widely popular, but overestimated its importance to voters. It turns out they didn’t want the government shut down to help even deserving illegal immigrants. It’s hard for the party of more government to lose an argument over who caused a government shutdown, but they managed to do it.