The thing about successful presidencies is there is an element of luck involved.

President-elect Joe Biden doesn't deserve any credit for Pfizer's Monday announcement that its COVID-19 vaccine appears to be effective — but he stands to reap the political benefits. If the vaccine is as effective as promised, and if it can be widely distributed to Americans during the coming months, the sense of emergency afflicting the country might subside over the next year. That, in turn, should help boost the economy back to something like normalcy.

Biden won't exactly be responsible for those developments, since the work of creating the vaccine and other therapies started well before his election, but that may not entirely matter. Voters might reward him and his party anyway. And Biden will have had the good luck to be president when those developments occurred.

There is some precedent for this kind of good political fortune — one involving the most-recent one-term president to be rejected by voters.

In 1992, Bill Clinton ran against then-President George H.W. Bush by campaigning incessantly against Bush's handling of the economy, which was still feeling the effects of a recession that had started in 1990. James Carville, a Clinton adviser, famously coined a slogan, "It's the economy, stupid," to ensure the campaign stayed on message. Clinton won the election, helped along by Ross Perot's third-party candidacy. The next month, the National Bureau of Economic Research announced that, actually, the recession had ended in March 1991.

That development has spurred rueful conservative counterfactuals for decades.

"Would the outcome of the 1992 election ... have changed if the NBER hadn't taken so long to announce the end of the 1990-91 recession???" Mark J. Perry of the conservative American Enterprise Institute wrote in a 2018 blog post. "Seems likely that George H.W. Bush would have certainly gotten a lot more votes, maybe even enough to win re-election?"

Clinton thus got an accidental head start on his presidency, then, taking office amidst a growing economy that turned into what was then the longest peacetime economic expansion in American history. Voters rewarded him with reelection in 1996. It can be argued Clinton deserves some credit for the country's prosperity during that decade, but let's be honest — he also got a bit lucky with his timing.

In politics, one person's good luck is another person's bad fortune. So it is for Joe Biden and the man he will replace, President Trump. It isn't actually Trump's fault that a once-in-a-century pandemic exploded out of China on his watch — and during an election year no less. And Trump is probably furious that Pfizer's announcement came on the Monday after Election Day, instead of the Monday before.

But it is difficult to feel sorry for the president. In the early days of the pandemic, many Americans were willing to give him the benefit of the doubt on his management of the crisis — Trump's approval rating, which has never been that high during his presidency, actually got a bump in the early days of lockdown, a sort of "rally around the flag" effect that accrues to presidential advantage during wars and other crises. But that support receded as it became clear that he mismanaged the response, downplaying the crisis, showing more interest in his ratings, diverting resources from blue states, and failing to lead on even the simplest of interventions, like wearing a mask and urging his supporters to do so.

So yes, President Trump had some bad luck. But he also made choices that compounded that bad luck.

Which means that if Joe Biden has the good luck to benefit as the pandemic subsides and the economy begins to grow again, he has the opportunity — depending on the makeup of the Senate — to make his own good choices. He has already started by listening to experts, and can build on that by staffing federal agencies with competent officials who can oversee smart distribution of the vaccine, rather than using his predecessor's method of putting incompetent loyalists in charge of the pandemic response. After that, Biden can push for policies that increase economic security for workers, broaden the country’s prosperity, and address climate change. It will not be enough to be satisfied that the emergency is over.

To his credit, Biden seems to understand that. And the truth is, if Biden gets lucky, it will probably mean that the country as a whole is doing better. The president's good fortune will be ours, as well.