COUNCIL BLUFFS, Iowa — President Trump was energized. Fresh from the fight to confirm Brett Kavanaugh, he was firing up thousands of supporters at a rally by complaining about how Democrats had treated his nominee and how they may yet try to remove Justice Kavanaugh from the bench. “They’re saying, ‘We’ll impeach him" Impeach him for what? For what?” The crowd booed.

“Besides that,” Mr. Trump then added slyly, “I have to go first, right?” The crowd laughed. But after almost two years of living under the cloud of a possible impeachment, it may soon cease to be a laughing matter.

While Democrats are largely ducking the topic on the campaign trail, few in Washington doubt that impeachment will be on the table if they win the House on Nov. 6. If that happens, anyone who thought the battle over Justice Kavanaugh’s confirmation was ugly and divisive should buckle up, because history suggests it would provide only a small taste of what lies ahead.