Great presidents are pragmatic. They realize that before great change can be effected, elections and re-elections must be won. Even Abraham Lincoln, dubbed "Honest Abe", knew this. A journal entry written in this community on April 15, 2015, the 150th anniversary of Lincoln's death, entitled Lincoln's Relevance Today, makes this point:
Lincoln was no saint. He was not a mindless idealist. On the contrary, a study of the man and his actions make it clear that he was first and foremost a pragmatist. He was a man of principle, to be sure, but he was practical and politically shrewd when it came to achieving those principles. For example, be believed in the rights enshrined in the Constitution, but he was not above restricting those rights when he felt doing so was necessary to achieve the greater good. He disallowed a free press when he believed that doing so would impede those seeking to break up the union. He removed the right of habeas corpus (judicial review for some of those arrested and detained) when he felt it necessary. When it looked as if he might lose a close election in 1864, he allowed leave to union soldiers in swing states so they could come home and vote for him. For Abraham Lincoln, lesser principles gave way in favor of the greater.

This has been true of all successful presidents. They have their eye on the big picture, their ultimate goal, one which will survive the test of time and one for which the citizenry will come to see that it was for the betterment of the nation. For Washington and Lincoln it was the survival of the union. For Theodore Roosevelt it was progressive reform that would protect the common man against the power of corporate conglomerate interests. For Franklin Roosevelt and Ronald Reagan it was emergence from economic hardship and the maintenance of global security. For Ulysses Grant and Dwight Eisenhower, it was preservation of the peace.
Many will disagree about the degree to which each of these presidents have achieved these goals. It is a measurement best taken through the lens of objective history, cleansed from the distortion of political ideologies and partisan politics.
Are there strategies or common characteristics that can be learned from the presidents who have achieved popular support and can these be applied generally or are they unique to their time? Here are some lessons learned from a study of presidential popularity:
1. Popular Presidents are great communicators. Franklin Roosevelt used his fireside chats to successfully bypass the media and Congress and speak directly to the people. Theodore Roosevelt cultivated a very friendly relationship with the media, something that William McKinley, Warren Harding (a former newspaper editor) and Dwight Eisenhower also did very well, but that William Howard Taft and Herbert Hoover never learned. Abraham Lincoln used communication in the press as a weapon in war (this story is very well told in Harold Holzer's excellent 2014 book Lincoln and the Power of the Press: The War for Public Opinion, reviewed here in this community). The jury is still out on whether or not Donald Trump's use of Twitter as a means of controlling the media agenda will be seen by history as a success or failure. Lessons will be learned from the 2020 election.

2. It's the economy stupid: This was a slogan used by the Clinton Campaign in 1992 to defeat a president who had once enjoyed a 90% approval rating. For Clinton, his success in turning deficit budgets into surplus budgets and the success of the dot-com economy kept Clinton's popularity high even as he was the subject of impeachment proceedings. While Presidents can not unilaterally control the economy, it had better be a president's first priority if he or she wants to win the hearts and minds of the electorate. However once again, a healthy economy will not, by itself, make a president popular, and once again, there are still lessons to be learned from the Trump administration which has a president with declining popularity presiding over low unemployment numbers and a very healthy stock market. Lessons are waiting to be learned by those who can set partisan sentiment aside in favor of objective study.
3. If you're going to war, you'd better win it, and quick: It was a prompt victory in the First Iraq War that catapulted George H. W. Bush to 90% approval ratings (only to have the air let out of its tires by the economy - see lesson 2). Early victory in the Spanish-American War, along with a strong economy, insured William McKinley's re-election. Conversely, lingering wars with daily reminders of casualty rates and lack of success contributed to the undoing of Lyndon Johnson, Harry Truman and George W. Bush. Military success can swell national pride, while loss of life in foreign wars where the objectives are unclear can deflate a president's popularity very quickly.
4. As much as possible, make peace with Congress: This one appears more difficult in the modern age when polarization in politics seems to be past the point of no return. But as history shows, this is not a new phenomenon. It dates back to the time of Alexander Hamilton and Thomas Jefferson, and was very prevalent during the antebellum period when the political polarization and resentment was sectional. Jimmy Carter went to Washington as a proud Washington outsider. While this position was initially popular, he soon found himself legislatively neutered and a one-term president. Harry Truman won an upset election in 1948 by campaigning against the "do nothing Congress", and while the strategy won him the White House, he left office with a record-low approval rating. Once again, it will be interesting to learn what history will show as the Trump Presidency continues its vocal criticism of those in Congress who fail to tow the party line.
5. Own up to mistakes: This was one of John F. Kennedy's greatest strengths. The nation quickly forgave him for the failed Bay of Pigs invasion after he took personal responsibility for its failure. Ronald Reagan left office with strong popular support despite his admission about his administration's participation in the Iran-Contra Scandal. Even after the Tower Commission personally cleared Reagan himself, he still took responsibility for his administration's actions, telling the nation:
“Now, what should happen when you make a mistake is this: You take your knocks, you learn your lessons, and then you move on. That’s the healthiest way to deal with a problem. You know, by the time you reach my age, you’ve made plenty of mistakes. And if you’ve lived your life properly — so, you learn. You put things in perspective. You pull your energies together. You change. You go forward.”

Presidential popularity and approval is a fickle friend. It can be lost by circumstances beyond a president's control such as world economic phenomenon or political forces. For those that manage to retain it, history demonstrates that their possession of it is anchored in a strong over-riding goal, the compromise of lesser principles for the greater goal, and an ability to get this message across directly to the people.
If history is an accurate guide to predict the future, the success of the current administration in 2020 will be tied to the maintenance of a healthy economy and keeping the nation out of foreign wars. It will also be based on the ability to communicate this message directly to the people. Leaving aside the potential for scandals or other similar impediments, if it fails in 2020, this will likely be the result of significant losses in this year's mid-term elections and a resulting lack of progress as a result of hostilities with Congress. Looking at the issue purely from the perspective of the study of history, divorced from any partisan or ideological distortion, there are still a lot of unknown factors which prevent accurate crystal ball gazing into 2020.

That's the wonderful thing about history: the more you know, the more you realize how much you don't know. And that's why it never gets boring.