The reason is the following simple point. The current Senate math suggests it is just possible—if almost everything breaks right—for Democrats to imagine potentially being in a position to govern the country in January 2021. Making plausible assumptions as I write this (Sinema in Arizona, Hyde-Smith in Mississippi, uncertainty in Florida), the Republicans will have a Senate majority in January 2019 of either 52 or 53.
Under current conditions of radical polarization, enacting any serious legislative agenda requires control of all three branches. That is even more true for any Democratic efforts to reform the political system in ways that make it less prone to minority rule—a federal statute protecting the right to vote, admitting new states such as Puerto Rico, limiting gerrymandering, enacting campaign finance laws compatible with current Court doctrine such as public financing, and so on. For Democrats to have any possibility of enacting such reforms in 2021, they will need a lot of unity and focus; they will need to win the presidential election; and they will need to net either +2 or +3 seats (at a minimum) in the Senate. Then they will need to enter the chamber in 2021 and immediately set rules that would protect the necessary reforms from filibuster. That is how a Democratic majority could use temporary leverage to put the brakes on minority rule.
This scenario is possible—but just barely. There are Republican incumbents in only a few purplish states facing the voters in 2020: Maine, Colorado, North Carolina, Arizona, Iowa. Meanwhile, Doug Jones (D-AL) will have a very uphill battle to retain his seat. So, under radically polarized conditions, the likely horizon of Democratic gains in a good year—and here we have to assume a year where Democrats are winning the White House—is just barely above the minimum required to regain a majority. If Democrats fail to win those races despite winning the votes of most voters in 2020, we will settle in for a considerably longer stretch of minority rule.
What will be absolutely unconscionable is if Democrats do manage to retake the Senate and White House in 2021, yet fail to use this temporary point of leverage to enact the kind of changes that would inch our system closer to majority rule.
(Original post here.)