Story highlights Ted Cruz suspends his presidential campaign after Donald Trump wins in Indiana

David Gergen: American voters need to sort out Trump's strengths and weaknesses

David Gergen is a senior political analyst for CNN and has been a White House adviser to four presidents. A graduate of Harvard Law School, he is a professor of public service and co-director of the Center for Public Leadership at the Harvard Kennedy School. Follow him on Twitter: @david_gergen. The opinions expressed in this commentary are his.

(CNN) Too often these days, we in the media like to proclaim that an event is "historic" when, in truth, it is a mere footnote. But after the Indiana primary, it really is true that historians will long be wondering whatever happened to American politics in the Republican presidential race of 2016.

For the first time in 75 years, a businessman with no prior political experience has virtually captured the nomination of a major national party . The last time this happened was when Wendell Willkie, head of a utilities holding company, stormed the GOP convention in 1940 , winning on the sixth ballot. Willkie went on to become a popular figure who ran a strong race against Franklin Roosevelt before eventually going down by 10 points.

David Gergen

There is, however, a far greater significance to Trump's rise to power than his business background; he is the most unconventional figure either party has put forward in modern times. And, while he will enter a general election as an underdog, chances are not insignificant that he could actually win the White House, entrusted with the most important and powerful office in a fractured world.

In the coming months, American voters -- not to mention those of us who toil in the media -- need to do some serious sorting out of both his strengths and his weaknesses. Because the truth is that as much as Trump has dominated the airwaves, we still don't know the man anywhere near as well as we should.

What is obvious so far is that millions of voters see in Trump a man of strength who can reverse our national direction -- in effect, a turnaround CEO. Frequently, voters turn to candidates whose strengths compensate for the weaknesses of the sitting president. Thus, we elected Jimmy Carter because he seemed honest, a sharp contrast to the Nixon years. Then we turned to Ronald Reagan because he was an antidote to Carter's vacillation. After eight years of George W Bush's plain talk, voters were inspired by Barack Obama's soaring calls. Now, after the Obama years and a string of broken promises by their own leaders, many Republicans believe Trump gets it and will act decisively to address their frustrations. That he is unconventional and outrageous says to them he is real, not a phony.

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