Game theory and the four magic words that will convict Trump.

More than two years ago, I kicked off this series on game theory and politics with a column called “Game theory and the two magic words that will impeach Trump.” Those two words were “and Pence.” The logic was that since then-House Speaker Paul Ryan yearned to be president, a movement to impeach both Trump and Pence at once would get Ryan, the next in the succession line, to join that movement. A cornerstone problem, though, was that Pence was not yet implicated in Trump’s impeachable actions.

But what a difference a “yet” makes. Pence is now highly implicated in the Ukraine scandal, which is the backbone of the House inquiry to impeach Trump. Pence is a target, and we’re likely going to find out he was much more involved in Trump’s mafia shakedown schemes. At minimum, Pence canceled a trip to Ukraine as a warning to the new president that they’d better play ball. At maximum, he’s been the bagman for Trump the whole time. Either way, his defense has been shallow and evasive, as if he didn’t think he’d ever be thrown under the bus by the president.

“I promise that pulling the gold cords doesn’t open a trap door in the floor, Mr. President.”

Pence is in a prisoner’s dilemma, a game theory concept that’s central to the original “and Pence” strategy. In a prisoner’s dilemma, two prisoners are given the options to cooperate with each other or betray the other. As it turns out, “betray” typically has the higher payoff for both participants.

Of course, it bears wondering: Is there any point to impeaching Trump if the Senate is just going to have a 30-second trial and acquit him? Or is there anything the Democrats can do to make it more likely that the Senate Republicans will observe their oath of office and actually convict Trump?

Don’t you think she looks … presidential?

I think there are four words that would make it significantly more likely. But the words can only come from one person. The responsibility bears on the rest of us to convince that person to issue them.

Those words are “I decline to serve,” and they must come from Speaker of the House Nancy Pelosi.

Here’s why: If the Republicans vote to convict Trump, and Pence was just as guilty, there will be a groundswell to remove him as well. As every schoolchild knows, when the president can’t serve, the vice president steps in. But when the vice president can’t serve, the president appoints a new one, subject to congressional approval—not Senate approval, the whole congress. If they’re both removed at the same time, possibly even in the same trial, the speaker of the House becomes president and appoints a new vice president. Since that’s Pelosi, that’s completely unpalatable to Senate Republicans. Especially if Pelosi might appoint Hillary Clinton as her vice president and immediately resign, making Hillary president. While that’s a highly unlikely scenario, it’s armageddon for Republicans. So they can’t support Trump’s conviction as long as it’s in play.

In another universe, President Albert soon wonders whether peanut farmer Jimmy Carter will primary his re-election campaign.

This is not the first time this scenario has come up. In fall of 1973, VP Spiro Agnew resigned after pleading no contest to tax evasion. That might’ve been the year’s biggest scandal had not President Nixon a mere ten days later fired special prosecutor Archibald Cox in the Saturday Night Massacre. With Agnew’s successor, Gerald Ford, facing a rocky confirmation by Congress, speculation turned to House Speaker Carl Albert—a Democrat from Oklahoma.

If Nixon resigned without a vice president being confirmed, Albert needed to know what to do should he become president. Speechwriter Ted Sorenson steeled his resolve with a legendary memo that explored all the possibilities Albert might face. Sorenson floated and then shot down the idea that Albert should appoint and then step aside for a Republican VP. Instead, Sorenson instructed Albert to throw out all the crooks left in the White House, lock down all of Nixon’s records for investigation, address Congress, and, above all, decline the opportunity to seek re-election. Sorenson urged Albert to say

“At no time did I seek this awesome burden; but I cannot shrink from my responsibility. Under the statute long ago considered with care and lawfully enacted by the representatives of the people convened in Congress, my election by the House of Representatives as Speaker placed me next in line for the high office to which I have now succeeded. Between now and January 20, 1977, I intend to fulfill the obligations of that office to the best of my ability. I shall not be a candidate for the Presidency in 1976 or at any other time.”

Nancy Pelosi remembers how wrenching Watergate was for America, which is why she’s never publicly backed impeachment until the Ukraine scandal made it impossible to avoid. (I think that was a rope-a-dope, but that’s immaterial for this point.) She’s in a powerful position: she can say the House speaker will decline to serve if the president and vice president are both convicted. Then the succession would move to the Senate president pro tempore, which is currently Iowa Senator Chuck Grassley.

Let’s chat about Chuck. He’s a Republican, sure. He believes what Republicans believe. But he’s a respected, uncorrupted politician. He’s 86 years old and he’s plenty likable. Look at his Twitter feed: It’s half University of Northern Iowa volleyball scores. How adorable is that? If you have to have a Republican in the White House, you’d take Grassley in a heartbeat.

Chuck Grassley likely doesn’t want to be president. But he would be if the other option was any of the fools and parasites currently in the White House. Beyond Pence, Secretary of State Mike Pompeo, Attorney General Bill Barr, and Energy Secretary Rick Perry are already embroiled in the Ukraine scandal, and Treasury Secretary Steven Mnuchin is right behind them. Education Secretary Betsy DeVos, HUD Secretary Ben Carson, Agriculture Secretary Sonny Perdue, and Commerce Secretary Wilbur Ross are mired in their own scandals. Transportation Secretary Elaine Chao is tangled in scandal with her husband, Senate Majority Leader Mitch McConnell (and, being foreign born, can’t serve anyway). About the only people on the succession schedule that might survive impeachment and the subsequent purge are Defense Secretary Mark Esper, Interior Secretary David Berhardt, and HHS Secretary Eugene Scalia, who haven’t been there long enough to wreck their agencies the way most Trump appointees do.

At 86, President Grassley’s not going to run for re-election, not after turning on Trump, anyway. Getting President Grassley installed gives the Democrats the most wide-open path to taking the White House in 2020. But weirdly, it also gives Republicans the most wide-open path to keeping the Senate, as they will not be saddled with an impeached and tyrannical child-president. Independents could vote for Republicans again and feel good about it.

The only way to get President Grassley is if Nancy Pelosi guarantees she will not assume the presidency if Trump and Pence are convicted. She should decline to serve, then let the ball roll. And the ball might roll in interesting ways. Emboldened by the possibility of losing the presidency to Grassley, Pence might turn on his boss, invoking the 25th Amendment. Barr might discover enough self-preservation instinct to open an investigation that he doesn’t quash. Perry, after removing the knife from his back, might tell all to Congress when he capitulates to his shiny new subpoena. Grassley might unexpectedly decide to spend more time with his family, making the next president… why, it’s Moscow Mitch McConnell, of all people. (He could be impeached with his wife!) All of this happens because the unthinkable outcome—President Pelosi—is taken off the table.

This is a game theory strategy called the optional prisoner’s dilemma. In the prisoner’s dilemma, both sides have only binary options; they must decide to betray each other or cooperate with each other. But “cooperate” and “betray” aren’t the only two options in some dilemmas. There’s also “abstain.” When a player in an optional prisoner’s dilemma abstains, they get what’s called the “loner’s payoff,” which isn’t the higher payoff of a winning player (if there is one), but it is a guaranteed payoff. The loner wins by not playing. As anyone who’s ever seen WarGames knows, when destruction is mutually assured, the only winning move is not to play.

There’s a cost, of course. Pelosi would be giving up the only shot she has to be president ever, and, if a resurgent Biden rallies people around Trump’s unfair attack, she would be giving up maybe the only shot we have to get a woman president at all. But there’s no indication she wants to be president, and she has only a very small shot—a moonshot, really—of achieving the White House this way. She undoubtedly knows it’s out of reach.

By abstaining from the battle over who gets to be president in the wake of impeachment, Pelosi and the Democrats can let the Republicans feed on each other. They’re already turning on each other over the president‘s shocking decision to abandon the Kurds in Syria to Turkey’s onslaught, so we know they can do it. We just need to give them the reason.

Pelosi’s been making all the right moves on impeachment lately. Can she make one more, designed to actually make impeachment matter? That’s unclear to me. But the winds are favorable: For the first time, according to a FOX News poll (!), 51% of Americans support both Trump’s impeachment and his removal from office.