For Democrats, the stakes for this year’s congressional elections have risen more dramatically than anyone could have foreseen even just a short time ago. All the weighty factors are still there—the Trump administration’s nepotism, corruption, and obstruction; its stacking of the judiciary; and its frenzied stripping of the bark off the welfare state. But after Donald Trump’s meeting in Helsinki with Russian President Vladimir Putin this summer, it has also become apparent that the president of the United States is an agent—or at least an overexcited fanboy—of a foreign adversary. And his party, despite occasional noises to the contrary, doesn’t seem inclined to do a thing about it. If ever America needed a big, earthshaking election to change the course of the country, it’s now.

Much of the time, in big, earthshaking congressional elections, Democrats have gotten hammered. First there was 1994, the so-called Gingrich Revolution, the year of the GOP’s Contract With America, when Republicans gained 54 House seats and took control of that body for the first time in 40 years. The country was dissatisfied with an economy that had yet to soar to the heights it did in the late 1990s and nettled by a sense that Bill Clinton’s presidency had meandered until the day Hillarycare finally crashed on Bob Dole Rock.

In a similar vein there was 2010, the year of the Tea Party revolt. This time, a Democratic administration managed to pass health care reform, but that just made Americans—or midterm voters, anyway—even madder than the 1994 failure. That and a lousy economy gave the GOP a net pickup of 64 seats and control again after a short, four-year Democratic regnancy. Finally came 2014. Maybe not big and earthshaking numerically, as the GOP gained just 13 seats, but it was depressing out of proportion to its numbers, as it ensured that Barack Obama would pass no major legislation during his final two years in the White House and that House Republicans would use that time trying to destroy Hillary Clinton. Plus, the continuing GOP Senate advantage meant Obama would have trouble with a Supreme Court nomination should a seat open up (how much trouble, no one could have imagined in November 2014).

Only once in the last three decades have Democrats had a satisfying midterm election in 2006, when they picked up 32 seats and won back House control for the first time since the pre-Gingrich days. Any George W. Bush agenda was dead in the water, and Denny Hastert, the GOP speaker who was not yet known as a child molester but who’d imposed that odious and polarizing rule about never bringing a bill to the floor that didn’t have a majority of Republican support, had been replaced by Nancy Pelosi. But even it wasn’t quite huge. Thirty-one seats were enough to change the signs on the doors, but it wasn’t the kind of thumping the GOP had given the Democrats in ’94.

For a taste of that, we must go all the way back to the midterm elections of 1974. The Vietnam War ground on, a year after Henry Kissinger won a Nobel Peace Prize for ending it. The OPEC oil embargo had come and gone, and gas prices—few Americans had ever given the price of a gallon of gasoline a moment’s thought before the fall of 1973—had more than doubled. And, of course, there was Watergate. On May 9, 1974, the House Judiciary Committee under Democratic Chairman Peter Rodino of New Jersey opened its hearings. Over the summer, it took testimony from a parade of Nixon aides and finalized three articles of impeachment in late July. In August, Nixon surrendered his tapes. Three months to the day after the Judiciary Committee hearings opened, Nixon resigned. He was at 24 percent in the polls. On September 8, new President Gerald Ford pardoned Nixon, which destroyed whatever goodwill Ford had earned. The Republicans were shipwrecked. There was so much blood in the water it was practically more blood than water. ...