President Barack Obama hopes to overhaul the tax code. That must mean he’s channeling Ronald Reagan again. He has continued to prosecute the war in Afghanistan. That means he’s taken a page from George W. Bush. He’s been willing to engage America’s opponents. That means he’s a carbon copy of Jimmy Carter.

But wait. He pushed his health care overhaul through Congress. That makes him different from Bill Clinton. He’s reluctant to levy new taxes to attack the deficit. That separates him from George H.W. Bush.

Now that we celebrate Presidents Day (the third Monday in February) rather than Lincoln’s birthday (Feb. 12) or Washington’s birthday (Feb. 22), we tend more than ever to look at presidents as a group, a subspecies all its own, and we measure our chief executives by how they conform with their predecessors and how they differ.

Presidential comparisons

So when we consider Obama’s speaking style, we compare him with John F. Kennedy; when we examine his attempts to forge international coalitions, we compare him with the first President Bush; and when we weigh his willingness to take on entrenched Democratic interests, we compare him with President Clinton. Sometimes the president does this himself.

Not so long ago he spoke privately with a confidant about how his communication style differs from Reagan’s. It wasn’t that he was trying to ape Reagan, as the newsmagazines have been saying. It was that he was trying to learn from Reagan, only to find that what Reagan had — a way of looking at the world that was instinctive, not intellectual — cannot be learned. In Reagan’s day, his partisans cried: Let Reagan be Reagan. Perhaps the lesson for Obama is to let Obama be Obama. But that’s another column.

Though presidents share many characteristics, they leave their own stamp on the office, reshaping it for all who follow. Consider how different William Howard Taft was from Theodore Roosevelt — a difference that proved fatal to Taft, who came in third when he ran for re-election — and how different Kennedy was from Dwight D. Eisenhower. In 1914, the radical journalist John Reed compared Woodrow Wilson in the White House with Theodore Roosevelt:

“There was none of that violent slamming of doors, clamor of voices, secretaries rushing to and fro, and the sense of great national issues being settled in the antechamber that characterized Roosevelt’s term in the White House. The window curtains swayed in a warm breeze; things were unhurried, yet the feeling in that room was of powerful organization, as if no moment were wasted — as if an immense amount of work was being done.”

No one wrote that about Warren G. Harding, or even about Reagan.

Hard to generalize

So it is not possible to make facile generalizations, such as saying American presidents are introverts (Richard Nixon was, Bill Clinton wasn’t); or that they are introspective (Calvin Coolidge surprisingly so, George H.W. Bush stunningly not so); or even intellectual (Obama is, Franklin Roosevelt wasn’t).

It’s not possible to say that they are people persons (Lyndon Johnson was, Wilson wasn’t); or that they are religious (Carter was, Reagan wasn’t); or that they are steeped in, and steered by, history (Kennedy was, George W. Bush wasn’t); or that they are formal in style (Nixon was, Ford wasn’t).

The best you can say is that most of them like golf (Eisenhower, the Bushes and Clinton especially) and that all of them since Franklin Roosevelt, who was stricken with polio after having an active early adulthood, were fit. Five of the last six presidents were joggers. I will leave it to others to speculate why two of the last five were obsessed with clearing brush, but surely there is a metaphor in there somewhere.

Though many presidents came from the legislative branch, a few months in the executive branch is usually enough to clear away the romance of Congress. Harry S Truman, a former senator, was contemptuous of the Senate, and Lyndon Johnson, known as perhaps the greatest master of the Senate, was even more so.

“The Congress has shown an inclination to treat a president with the same kind of consideration it extends to our birds and other wildlife,” said Coolidge, a former governor, after Congress appropriated $48,000 for a presidential retreat.

The late presidential scholar Richard Neustadt used to say that the president possesses little more than the power to persuade, and recent presidents have discovered the limits of that particular power, which is not delineated in the Constitution.

“Presidents think they can move the public,” George C. Edwards, who holds a chair in presidential studies at Texas A&M University, said in an interview. “They just won an election. They think they are very persuasive fellows. But when it comes to taking your case to the public, they almost all fail all the time. That’s because there’s opposition to anything significant. The public never pays attention. The public’s views are only reinforced, seldom changed. And when the public does change views, it’s not because the president has persuaded them. It’s because the world has changed — because, for example, the Nazis are marching across Europe and maybe we ought to re-examine isolationism.”

Complicated lives

But presidents also live complicated lives. Wilson watched from the sidelines as the Clayton Antitrust Act was passed because his wife was dying. John Tyler’s wife died in the White House. William McKinley spent a good deal of his presidency ministering to his ailing wife. Coolidge’s son died while he was in office. Kennedy’s wife gave birth to a son nearly six weeks early only to see him die two days later.

“Presidents are people, too,” Kenneth M. Duberstein, who was Reagan’s chief of staff, said in an interview. “They have families, they have needs, they have hobbies, they have hobby horses. Is it normal to go see your kids play basketball on a Saturday morning? Damn straight. Is it nice to go back home? Of course it is. Presidents do those things. The problem they have is that they are in a bubble. They don’t walk through the front entrances anymore. They enter hotels through kitchens. That’s the thing people forget. The president is not supernatural.”

That, as we mark another Presidents Day, may be the main thing all presidents have in common.

— David Shribman is executive editor of the Pittsburgh Post-Gazette.