If you are under the age of 30, you would be forgiven for believing that, yes, as a rule the person already inhabiting the White House is always the odds-on favorite to be elected to a second term. That’s because all three presidents you can really remember—Bill Clinton, George W. Bush, and Barack Obama—rather handily won re-election. 

“The power of incumbency is not to be sniffed at,” said Margaret O’Mara, a professor of history at the University of Washington, who now studies presidential politics and the intersection of economic and political power. 

But look back further and you’ll see that a second term hasn’t always been a sure bet. Only 17 of 44 presidents have been elected twice, a success rate for re-election of roughly 38%. And it’s rare for two-term presidencies to run concurrently. A streak of three in a row was repeated only once before in the early days of the Republic by Thomas Jefferson, James Madison, and James Monroe. 

The trend toward second terms in recent years is not random, but a consequence of a consolidation of power in the Executive Branch, said O’Mara, who was previously a policy adviser to then-Vice President Al Gore.

“I think it has shifted because the presidency itself has gotten more powerful—much more powerful than the founders intended,” she said. “One of the reasons we can’t remember much about Rutherford B. Hayes or Benjamin Harrison is that the presidency did not loom as large back then. The parties, Congress, and the courts had much more heft 100 or 150 years ago—and the presidents were less imposing figures, with a few exceptions, Lincoln being one of them.”

Circumstances changed in the 20th Century, as presidents from Roosevelt and Eisenhower to Reagan and Obama harnessed their unique powers as commander-in-chief, the platform provided by mass media, and an increasingly fractious (and thus weaker) Congress to expand the reach of their office. 

The ability to drive the news cycle has been especially critical, and it’s an area in which Trump, love him or hate him, undoubtedly excels.

“As President Trump has demonstrated with frightening clarity, presidents dominate the national and media narratives; we see or hear them daily, in Trump’s case often hourly,” observed Aaron David Miller, a senior fellow at the Carnegie Endowment for International Peace, in a recent essay entitled “The Power of Incumbency.” 

“They wield the powers of government; their policy priorities and re-election campaigns are launched even before their first term begins; and that initial success not only creates an existing campaign organization and donor bases but can also drive the perception that the election is theirs to lose,” Miller concluded.

One way for a challenger to overcome those odds is the economy, as in 1992 when Bill Clinton beat George H.W. Bush, with an assist from Ross Perot. On that score, at least for now, Trump has the upper hand.

Coming off a year in which the S&P 500 returned a whopping 28.9% and the Dow Jones Industrial Average rose by 22.3%, the strength of the economy may well persuade voters to stay the course.

“That’s a big headwind for a Democratic candidate to message against,” O’Mara said. Trump has thus landed in a position that is somewhat the inverse of the elder Bush’s.

Bush was a leader voters largely respected, yet they dropped him when they felt economic anxiety. Trump faces high disapproval ratings, yet a second term remains viable for him if voters decide their top priority is to preserve the economic status quo. In this way, Trump’s path could resemble that of Bill Clinton, who overcame high negatives and questions about his leadership by touting a resurgent job market. 

“It is interesting that modern America has put such a premium on presidential personality and character and conduct when talking about candidates but, at the same time, when it comes down to it, people routinely vote based on economics,” O’Mara said.

If ‘92 isn’t a match, “1984 is an interesting year to think about,” O’Mara continued, “though it’s not a great comp if you’re a Democrat.”

In ‘84, of course, the once-divisive Ronald Reagan rode a message of optimism and patriotism to a landslide victory over Walter Mondale, a seasoned, serious, and down-to-earth former vice president who sounds a bit like you know who. 

What’s odd about the 1984 example, though, is that “the economy for most of Reagan’s first term was the pits,” O’Mara said. “Democrats had a powerful argument that things are not working, but the case for ‘Morning in America’ resonated with the way voters saw things trending.”

The opposite scenario could potentially play out this time: If voters begin to think the economy, dragged down by weakness in the manufacturing sector, is trending in the wrong direction, Trump could suddenly find his support evaporate.

The election of 1976 offers a third template. Jimmy Carter, a relative unknown on the national stage, emerged from a crowded Democratic primary field by pledging to restore the dignity of the Oval Office. He engineered a spectacular upset victory in part because his opponent, Gerald Ford, was never able to shake off the perceived original sin of his presidency, which was the pardon of Richard Nixon.

Though the economy in 1976 had finally broken out of the recession of the previous three years, the recovery didn’t come soon or fast enough to rescue Ford. And Ford, unlike Trump, lacked some of the power of an incumbent in that he had never been elected to national, or even statewide, office on his own. Plus, many key members of the brain trust that had put together the GOP’s recent victories were unavailable to work on the campaign as they were recently incarcerated, yet another parallel to 2020.

Impeachment, of course, is a huge wild card. And we still do not have a clear understanding of when (or even if) a trial in the Senate will happen in the coming weeks. 

Then there is the conflict with Iran, which has the potential to escalate quickly and in unpredictable ways. 

Though foreign policy rarely plays a decisive role in U.S presidential elections, it is not unheard of. In 1968, for example, the deteriorating situation in Vietnam crippled Lyndon Johnson’s re-election chances, and prompted violent anti-war protests at the Democratic National Convention in Chicago.

On the Republican side, Nixon, a flawed but canny campaigner, outlasted primary challenges from Reagan, Nelson Rockefeller, and George Romney. Though the  economy was buoyant, discord over the war ultimately proved to be too much of a political albatross for Vice President Hubert Humphrey, and Nixon won.

Not to say that the best case scenario for Democrats is to find their own version of Nixon, but events are moving fast. The main thing to note about 1968, O’Mara said, is just how truly insane was the progression of landscape-altering developments unfolding in staccato fashion on almost a weekly basis, from Prague Spring and the Tet Offensive to the assassinations of Martin Luther King Jr. and Bobby Kennedy.  

“Incumbency is an incredibly powerful factor and more powerful over time as the presidency itself has gotten more powerful,” O’Mara said, “but you have to take everything the experts say with a grain of salt in the age of Trump.” 

“We can say here are the rules, here are the patterns, here are the historical precedents, but you can never predict what will happen,” she said. “And especially at a time like this, there are no clear-cut analogies.” 

Correction, January 29, 2020: An earlier version of this story incorrectly stated that no other President had been impeached during their first term. President Andrew Johnson was impeached during his first term in 1868.

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