I teach a course at the University of Chicago on presidential elections, and I hear the same kind of question from friends on both the right and the left. The Republicans I grew up with in western Kansas cannot understand why Donald Trump is not far ahead in the polls, whereas the Democrats who surround me in Chicago wonder how it can possibly be that Kamala Harris is not running away with the race.

These are the right questions for understanding contemporary US politics. For all its unusual aspects -- not least Harris’ sudden appearance as the Democratic standard-bearer -- the dynamics of the 2024 campaign, like the two that preceded it, are typical of presidential elections going back at least 80 years. But two features of this campaign do represent a significant departure from decades of historical experience. The first is cause for consternation among Democrats, and the second is a source of frustration for Republicans.

Start with the Democrats. Consistent with historical precedent, the nominee of the party that controls the White House is facing strong electoral headwinds. If Harris wins, she will be the first nominee of the incumbent party in 76 years to be elected despite a presidential approval rating below 50 percent at the time of the election.

Since polling began in the early 1940s, the only nominee to win under such circumstances was Harry Truman in 1948. He had a 40 percent job approval rating (though this was last measured 4 1/2 months before Election Day). Since then, seven candidates have tried to outrun an unpopular incumbent of the same party, and seven have failed, most recently Trump himself, whose approval rating on Election Day in 2020 was 46 percent. President Joe Biden’s approval rating (according to Gallup) is currently 39 percent, six points below Harris’ approval as vice president (45 percent).

The relationship between presidential approval ratings and election outcomes underscores the conventional view that elections are referenda on the performance of the party in power. The problems that have beset Biden abroad (Ukraine and Gaza) and at home (migrants crossing the southern border) have raised concerns in voters’ minds. Biden has also presided over an election-year economy that has been good by some measures (growth in gross domestic product) but not very good by others (growth in personal disposable income).

Voters may well be myopic or overestimate the control a president has over complex systems like the economy, not to mention the decisions of ordinary people and world leaders. It is typical for voters to mete out too much blame for bad times and to give too much credit for good times. Either way, the president -- and presidential candidates -- can do little to affect such judgments. In politics, as in many endeavors, it is better to be lucky than right.

Thus, Harris is not running away with the 2024 election because the “fundamentals” that structure elections are unfavorable to the Democrats as the party of the incumbent. The difficulties that Harris has had in pulling ahead are perfectly explicable as the normal pattern of US presidential elections.

Trump, on the other hand, has managed, to an unprecedented degree, to center elections on himself, thrilling many voters while appalling many others. In 2016, Hillary Clinton was the most unpopular presidential nominee in recent history, except for Trump. Moreover, the resistance to Trump has remained consistently high, with his unfavorability rating exceeding his favorability rating since 2016.

Similarly, Trump was extraordinarily unpopular as president. He is the only chief executive whose Gallup approval rating never cracked 50 percent while in office. His average job approval of 41 percent was the lowest ever, four points below Jimmy Carter’s.

Never in history has the candidate himself been so central. Even Ronald Reagan, renowned for his popular appeal, did not dominate elections the way Trump has (both to his advantage and to his detriment) through his personality. Reagan achieved his victories in 1980 and 1984 in circumstances much more favorable to his party; his “charisma” was more the effect of his electoral success than its cause.

The resistance to Trump began within his own party. Republican officeholders withheld their support until he had wrapped up the 2016 nomination. Republican-leaning newspapers endorsed his opponent or no one at all, and most Republicans in leadership were wary of his demagogy, incendiary rhetoric, rejection of long-standing Republican policy principles and personal faults and deportment. Most came around to him, but some did not.

Others grew alienated during the grueling experience of the Trump presidency. For some Republicans (and independents), the last straw was his loyalty to himself over his party and country when it came to endorsing candidates and dealing with foreign allies and adversaries. For others, it was his pandering to evangelicals, his embrace of isolationism, and his indulgence of racist white nationalists. For still others, it was his attempt to steal the 2020 election, culminating in the uniquely shameful attack on the US Capitol on Jan. 6, 2021. Most Democrats and many independents, of course, have resisted Trump from the start.

Thus, the reason Trump isn’t running away with the 2024 election is Trump himself. It is difficult to escape the conclusion that the Republicans would be the favorites in a normal year with a normal candidate. But 2024 is not a normal year, because Trump is not a normal candidate.

The American electorate’s decision is being influenced both by the quotidian concerns that usually structure election outcomes and by one outsize personality. Never has the latter been such a key consideration. Hundreds of thousands of voters -- perhaps millions -- are putting aside their party loyalty, policy priorities, and complaints about current conditions to stand against a candidate they consider unfit for the presidency and unworthy of election. We will soon know whether politics as usual or unusual politics will carry the day.

John Mark Hansen

John Mark Hansen, a professor of political science at the University of Chicago, is a former coordinator of the research task force on the federal election system for the National Commission on Federal Election Reform. The views expressed here are the writer‘s own. -- Ed.

(Project Syndicate)