For the first time in a decade, Democrats have effective control of all three levers of lawmaking power in Washington: the House, the Senate and the presidency. And soon we’ll find out just how powerful that arrangement will be. New Senate Majority Leader Charles E. Schumer (D-N.Y.) and Senate Minority Leader Mitch McConnell (R-Ky.) are locked in discussions about how the new 50-50 Senate will function, in which the most consequential point of contention is one thing: the filibuster.

The moment marks the culmination of years of a building liberal effort to get rid of the filibuster and its 60-vote threshold. Even past supporters of keeping the filibuster, like Barack Obama and former Senate majority leader Harry M. Reid (D-Nev.), have said ending it should be on the table. And given Senate Democrats need 10 GOP votes to pass most legislation under current rules, plenty are arguing the time is now.

But there are plenty of compelling — mostly practical — reasons to approach such a change cautiously.

The first is what it might open the door for — both the good and the bad. Proponents of dumping the filibuster argue that Democrats shouldn’t squander an opportunity to pass an agenda at such a pivotal moment, especially as the administration combats the dueling problems of the coronavirus pandemic and the accompanying economic downturn. The New York Times’s Ezra Klein makes just such an argument.

But it’s also worth considering what this would mean both in the near term and, potentially, just a few short years. The Democrats’ narrow Senate majority provides some impetus for nuking the filibuster, because of the sheer number of GOP votes that would be needed for most legislation: It’s a lot easier to pick off four votes if you have a 56-44 majority than it is to pick off 10 in a 50-50 Senate. It’s very easy to see the Senate descending into one of its most gridlocked periods in an era already marked by gridlock.

The Democrats are taking control of the Senate as an impeachment trial, cabinet nominations and an ambitious Biden agenda are all on the table. (The Washington Post)

That 50-50 split, however, might also negate much benefit from getting rid of the filibuster. Yes, they could pass everything with 50 votes given Vice President Harris will break ties. But if Republicans vote in unison, Democrats could afford precisely zero defections. Sen. Joe Manchin III (D-W.Va.) comes from one of the reddest states in the country, and Democrats could also struggle to win votes from more moderate senators like Kyrsten Sinema (D-Ariz.) and Jon Tester (D-Mont.), or others who face reelection in tough states, like Sens. Mark Kelly (D-Ariz.) and Raphael Warnock (D-Ga.).

Manchin in particular looms as a tough vote for anything amounting to a truly bold, left-leaning agenda. On top of that, Democrats have few votes to spare in the House, with just a 10-seat majority — plenty of representatives are like Manchin and Tester, answering to conservative constituencies — meaning there will remain obstacles to big change, even within the party.

The 2022 elections also loom large: They could well install Republicans back in control of the Senate and the House. Midterms are generally very tough on a president’s party, and Republicans need only the most modest of gains to take back both chambers. Some Democrats see this as an argument for going bold and dumping the filibuster now — time being of the essence — but it also means rolling back the most significant impediment to legislating could quickly boomerang.

And on this count, Democrats need to consider how our politics are set up. The fact is, despite Democrats’ current control, Republicans have inherent advantages when it comes to winning all three levers of power — and could just as soon reclaim the full control they had until two short years ago.

Since 2000, Republicans have won the popular vote in a presidential election once, but the electoral college has delivered them two additional victories. And in both the House and the Senate, our population is distributed in a way that also gives Republicans more representation than their raw votes suggest.

Despite Donald Trump losing the popular vote in 2016, for instance, 30 of 50 states went red. He lost the popular vote in 2020 by more than four points, but still won half of states. That bears on the Senate. And throwing the GOP’s control of redistricting in most states on top of how our population is distributed has also given the GOP a big edge in the House.

Only twice in the past 20 years have Democrats had more House seats than their share of the popular vote would dictate, according to data from FairVote. After the last round of redistricting before the 2012 election, Republicans in three consecutive elections won at least 20 more seats than their share of the popular vote would suggest. They also control more of the upcoming gerrymandering process than Democrats, and while that control is less pronounced than a decade ago, it could well allow them to restore much of that advantage.

The fundamentals of our politics are continually shifting, and these advantages could wane over time. But while the Democrats control the trifecta right now, if one party seems more likely to exercise complete control in the near future, it would be Republicans. Even if they can just consistently get to even on the popular vote, they could well control all of Washington.

There is one very compelling rebuttal to this: The idea that the filibuster is on its way out anyway. Reid has said the end of the filibuster is a matter of when, not if. In 2013, when he was Senate majority leader, Reid nuked it for non-Supreme Court judicial nominees in the face of a GOP blockade. Then, in 2017, the GOP under McConnell got rid of it for the Supreme Court so that they could confirm Neil M. Gorsuch. Who’s to say it won’t continue to be eroded when it suits the party in power, and that the party that kills it won’t be the Republicans. The argument is often accompanied by the idea that, if the bare-knuckled McConnell were in Schumer’s shoes right now, he wouldn’t hesitate to take this step.

It bears noting, though, that McConnell was in something amounting to Schumer’s shoes four years ago. While he nuked the filibuster for Supreme Court nominees, he didn’t do so for everything else. And it would have been fruitful; the GOP at the time held the Senate and had both the presidency and a sizable House majority. Trump even pressured McConnell to do it, but it didn’t happen. Perhaps it was less feasible then, and perhaps he’d have a different view today, but it’s not necessarily inevitable once roles are reversed.

There’s one clear reason for that: This isn’t just up to Schumer or McConnell. They need to get enough votes to change the rules, and that’s hardly a given. Even if Schumer wants to do this, Manchin said flatly after the election, “I will not vote to do that.” In 2017, fully 61 senators from both parties signed a letter in favor of keeping the legislative filibuster. Many of them have shifted since then, particularly the Democrats. But only a handful — and in today’s case, only one — is needed to prevent such a change.

Could McConnell marshal enough votes if and when the opportunity presents and if he pushes it hard? Perhaps, but there were 28 Republican senators on that letter, even when they were set up to dominate the agenda by taking the opposite position.

Given all of that, the most immediate question isn’t really whether Democrats will nuke the filibuster right now, which they probably can’t do even if they wanted to. The real issue is whether and how they will preserve that option in case they determine, in the months ahead, that Republicans are obstructing too much. McConnell is pushing Schumer to take such a change off the table — to guarantee the filibuster won’t be nuked.

Agreeing to those terms appears nearly impossible for Schumer, given the growing thirst in his base for a filibuster-free Senate. He said Friday that such a guarantee is “unacceptable — and it won’t be accepted.”

But the outcome and its particulars are important, given how consequential this change would be for the future of American politics. It would surely be one of the most significant developments in modern political history.

Thus, Democrats need to balance their desire for immediate gratification — and just how much actual gratification it would provide — with what it might mean for the near future of their party.