The Democrats swept to power in Congress by campaigning in a way that has been successful for Democrats for generations. “Republicans will take away your health care,” they said, after having focus-grouped it. Now we are preparing for a 2020 campaign in which Donald Trump and Republicans can as easily advertise to the public: “Democrats will take away cows, and your car.” What happened to Democrats? Back in November, it looked like Nancy Pelosi and the Democratic House caucus had found the perfect plan for their party in the era of Trump: Avoid talking about impeachment and stick to simple...