There’s been more talk than usual among 2020 Democratic presidential candidates about their “theory of change”–how they will implement their proposals. But there’s still a hole in the discussion, which I discussed at New York after the first night of candidate debates:

Like a lot of political obsessives, I came up with my own question I wanted to hear posed to the Democratic candidates debating on Wednesday and Thursday nights:

“One highly relevant question the 20 Democratic presidential candidates who are debating this week might be offered is this: Do you have a plan B for the agenda you will pursue if Republicans retain control of the Senate?”

Well, on the first debate night, to my shock, two moderators went there. First, Rachel Maddow asked Cory Booker this question:

“Senator Mitch McConnell says that his most consequential achievement as Senate majority leader was preventing President Obama from filling a Supreme Court seat. Having served with Republicans on the Judiciary Committee, do you believe they would confirm your court nominees?”

Booker hemmed and hawed and then said he was confident Democrats would win the Senate in 2020 (not a strong bet, actually), an assertion that Julián Castro had made earlier. Asked the same question by Maddow, Bill de Blasio was slightly more responsive:

“[T]here is a political solution that we have to come to grips with. If the Democratic Party would stop acting like the party of the elites and be the party of working people again, and go into states, including red states, to convince people we’re on their side, we can put pressure on their senators to actually have to vote for the nominees that are put forward.”

This suggests some sort of political transformation that is very unlikely in the wake of what is sure to be a bitter, closely fought election. It’s precisely the sort of argument Barack Obama made in 2008 about how he’d overcome Republican obstruction, and he struggled against McConnell even with an initial supermajority in the Senate.

Then Chuck Todd asked Elizabeth Warren a more direct and general question:

“It’s very plausible that you’ll be elected president with a Republican Senate. Do you have a plan to deal with Mitch McConnell?”

Warren responded instantly: “I do.” But she really didn’t.

This often practical-minded senator, who by my account was the overall debate winner, gave it a good try, saying she’d call on her supporters to stay engaged and never stop fighting. The saturnine Mr. McConnell could not possibly care less….

Todd tried asking John Delaney about dealing with McConnell, and as usual he talked about bipartisanship, but didn’t have any insights for winning Republican votes in the Senate beyond calling for “ideas that work.” Todd went back to Booker, who managed to come up with the unicorn of an underwhelming bipartisan criminal-justice-reform bill in 2018 as though it offered some sort of template. Criminal-justice reform, of course, is a cause that developed a grassroots conservative constituency over a long period of time. If there’s some similar area where both parties are already poised to come together, I don’t know where it is.

Now the truth is, there are no easy answers to Maddow’s and Todd’s questions about McConnell. But there are plausible approaches: (1) You can aim at picking off one or two Republicans with the kind of public pressure that Warren (and Sanders and de Blasio) like to talk about, and hope for the best, following the example that saved the Affordable Care Act in 2017 when Republicans could not hold their own conference in line; (2) you can focus on executive actions — Amy Klobuchar should have busted into the discussion of a Republican Senate and drawn attention to her vast agenda of executive orders and agency policies she has already promised to implement during her first 100 days in office; or (3) you can promise to lead a holy crusade to retake the Senate in 2022 if Republicans obstruct the new president’s agenda and maybe build a durable Democratic governing majority.

But just promising to fight is not going to strike fear into Mitch McConnell’s dark, hardened heart. The candidates ought to think more deeply about this problem, because it could be more important than anything else the winner encounters.