Biden is out. Now comes the hard part.

We know that America’s two main political parties have very different approaches to public policy. But this historic moment highlights a staggering difference in how the parties pick and treat their leaders.

To call Joe Biden’s withdrawal unprecedented is to really sell it short. Yes, there have been cases (including Harry Truman in 1952 and Lyndon Johnson in 1968) where presidents have been encouraged by aides and party officials to withdraw due in part to their unpopularity. But those decisions were made long before the candidates’ respective conventions, and with plenty of time for interested party actors to decide on whom the next nominee would be.

By contrast, the Democrats have already done the real work of the 2024 nomination. In 2019-2020, the Democratic Party, defined broadly, vetted Biden along with dozens of other candidates through a lengthy series of primaries and caucuses, debates and speeches, meetings, negotiations, and more. Ultimately party insiders determined that they had the most faith in Biden’s ability to both defeat Trump and work toward party priorities on the economy, the environment, labor, student loans, and more. The party’s voters and convention delegates concurred.

The lack of a real Democratic Party nomination contest in early 2024 was a sign of another decision; the party remained comfortable with Biden’s progress on the goals it cared about and thought he could continue to work toward those goals in a second term. And again, the party’s voters concurred, and presumably the convention delegates were prepared to re-nominate him.

Certainly, prominent people within the party who once thought Biden could win now aren’t so sure. Some voters, too, seem to have changed their minds. But the idea that there can be some sort of final veto stage of this process, after the formal primaries and caucuses are over, is novel — and a little stunning.

Contrast this with the Republican Party. Party leaders did not want Donald Trump to be their nominee in 2016, but they ultimately pledged loyalty to him once he won the nomination. They have now functionally nominated him in three consecutive cycles. And any time new damaging information comes out — poor election performances in 2018, 2020, and 2022; helping organize a coup rather than leaving office peacefully; two impeachments; indictments in four separate criminal trials; conviction on 34 felony counts; a multi-million dollar fraud ruling; a court determination that he is liable for sexual abuse; a vow to “terminate” the Constitution, etc. — it only causes the party to support him more.

Democrats abandoned their octogenarian leader for seeming cognitively enfeebled and unpopular; Republicans doubled down on their septuagenarian leader for a track record that has gotten increasingly worse with each passing month.

Now, the Democrats have work to do. In order for this decision to be proven clever, and not catastrophic, what comes next in the process has to be far better thought out then what came before. If Vice President Kamala Harris is able to swiftly consolidate party support, reassure the constituent groups that were comfortable with Biden that she’d be at least as good on the issues they care about and impress voters and political observers that she has the ability to “prosecute” (her words) Trump in an effective way that brings in votes, this may turn out to be a good use of media pressure and party power.

It’s also entirely plausible that Democrats will descend into a massive factional squabble at the Democratic National Convention in Chicago, leaving all sides demoralized. In this scenario, Republicans will likely enjoy an even easier election than they would have had otherwise. (We’ve seen that before!)

In other words, whether Biden’s withdrawal was a historically good or a historically bad move depends heavily on what comes next. But no matter what happens, it was certainly historic.