Democrats had just obliterated Republican control of three Philadelphia-area suburban counties late Tuesday night in a stunning rebuke of President Donald Trump when, amid a deafening celebration in Swarthmore, I pulled aside the chairwoman of the party whose incensed liberals had just toppled one of the most formidable GOP machines in the United States.

This was an incredible scene: Colleen Guiney’s infantry of newcomers to the political system had just seized every County Council seat, the post of district attorney, and a full slate of judgeships in Delaware County. They left not even a crumb for the GOP, annihilating Republicans with the brutal finality of a nuclear bomb. And this in a county where, for generations, you had to at least pretend you were Republican if you wanted to get anything done.

Democrats in Bucks and Chester Counties waged similar massacres, albeit against machines with less legendary staying power. Given how all three counties are jam-packed with voters from both parties, they are central in delivering or denying presidents the White House. The big question — the one I asked as I stood with everyone at the Inn at Swarthmore victory celebration — had everything to do with 2020.

“What message," I asked Guiney, “would you like to send Donald Trump tonight as we stand here in Delaware County?”

Although the leader of Delco Dems for just 17 months now, the pediatric nurse-practitioner zeroed in quickly on a four-word answer.

“His days," she said, "are numbered.”

What’s extraordinary after last night’s wins, beyond the wins themselves — Delaware County has been under Republican control since the Civil War — is the way a single president has mobilized a formerly anesthetized electorate, so that what we seem to now have is a fully engaged two-party system.

Anger, it turns out, can be a positive thing for democracy, just as it can be toxic.

Democrats, despite having secured a sizable voter majority in Delaware County in recent years, had been unable to seize control from Republicans. They made their first breakthrough in 2017 by winning two of its five County Council seats, all of that fueled by anti-Trump rage.

But for years prior, they had been impotent against the GOP, due in large part to their party’s overall disengagement on the ground level in municipal and county elections across Pennsylvania.

Democratic organizing and voter engagement had been pathetic to nonexistent in many communities before Trump came along. Republican incumbents would face weak or no challengers. Democratic voters were like self-satisfied zombies who trotted their half-conscious selves out to polling places only in sexy presidential election years.

Then came Trump in 2016. Talk about smelling salts.

Hillary Clinton did well enough in Southeastern Pennsylvania against Trump in 2016, but didn’t drive high enough voter turnout to offset his gains elsewhere in the state. Supercharged turnout in local races since 2016 is expected to be a key weapon against Trump in 2020.

What we saw Tuesday, as we saw in county elections in 2017 and state legislative races last year that generated huge wins for Democrats, is that Democrats are now fully awake in Pennsylvania. They get that you don’t win in politics by being a short-term thinker with just a fiery Twitter finger. (Democrats knocked a ton of Republicans out of the state House and Senate last year, thinning the formerly implacable GOP majorities in Harrisburg who control congressional redistricting and public school funding policy.)

You must sweat. You must work. You must knock on doors and dominate from the ground up. The Dems now get this.

On Tuesday, with a 48% to 39% registration edge over Republicans, they finally grabbed the golden ring.

The result, at least according to one preliminary estimate: Turnout in Delaware County on Tuesday was in the ballpark of 150,000 people — a 25% increase from the record-breaking turnout fueled by Democratic rage in 2017, said former Democratic county party chief David Landau.

I bumped into Landau in a crowded, sweaty, and jubilant Inn at Swarthmore ballroom as the victory party got underway around 11 p.m. Next to Landau was Democratic Attorney General Josh Shapiro, who I heard talking to the old-head Democratic activist about big wins that also were flowing in from neighboring Chester and Bucks.

“So cool,” Shapiro told Landau.

Landau, who has worked for 35 years to topple Delco’s Republican machine and only stepped away from the chairmanship 17 months ago, was on Cloud Nine.

“I thought we would win by 8[,000] or 9,000 votes,” he told me as the three Democratic women who won council seats fired up the crowd with victory speeches. “We won by 15,000 votes. That’s just a deluge.”

When I talked later to his successor, Guiney made a point to credit Landau for a lifelong pursuit that may have seemed like a fool’s errand until now.

“There are people who have been waiting to see this happen their entire lives,” Guiney said. “I’m grateful for all the work they did in all the years when it didn’t seem possible.”

On Tuesday, the impossible became real. Democracy is alive in the Trump era, after all.