When Barack Obama accepts the Democratic Party’s nomination for president, he will deliver his speech the way John F. Kennedy did in 1960: in a stadium.

The image of a stadium full of people waiting to hear a speech—a political speech, no less—underscores a somewhat overlooked aspect of the American scene: Speeches matter. In a day when comments muttered into an open microphone, or a distasteful joke captured on YouTube (macaca!) can alter the course of a campaign, it’s still the vision and policies outlined in speeches that shape our political landscape.

Enter Michael A. Cohen, a professional speechwriter, who chronicles the history of notable speeches by presidential candidates in his aptly titled Live From the Campaign Trail. The book collects more than 20 speeches, delivered by Democrats and Republicans from 1896 all the way up to Bill Clinton’s "I still believe in a place called hope" in 1992. (In the epilogue, Mr. Cohen pays belated homage to Mr. Obama’s speech-making skills, and also refers to Hillary Clinton as "somewhat rhetorically challenged.")

This is a perfectly timed compendium for anyone skeptical about the power of rhetoric during a campaign, or (come on, admit it!) anyone who’s been completely mesmerized. Mr. Cohen draws upon a rich context, from news accounts in The New York Times and The Nation at the turn of the century to interviews with J.F.K. speechwriter Ted Sorensen.

Delegates waved hankerchiefs, hats, umbrellas, and anything else they could get their hands on. Those in the galleries tore off their coats and flung them from the balconies into the gurgling crowd. Grown men hugged and openly wept as tears streamed down their bearded cheeks," Mr. Cohen writes.

The year was 1896, the subject was gold standard vs. silver standard, and the speechmaker was William Jennings Bryan—who went on to lose the election.

Prefacing each of the abridged speeches included in the book is a helpful primer to the political context with which they were given. And it’s here that Mr. Cohen provides his most useful insights. For example, he explains that Mario Cuomo’s "captivating rhetoric" during the Democrats’ 1984 national convention simply "wasn’t a recipe for political success."

After describing how Mr. Cuomo invited President Ronald Reagan to visit "Appalachia, where some people still live in sheds," and "Lackawanna, where thousands of unemployed steel workers wonder why we subsidize foreign steel," Mr. Cohen writes, "Again, Cuomo was highlighting real problems and concerns, but were these places with which most Americans could identify?"

Mr. Cohen goes on to argue that Mr. Cuomo and his fellow convention speech maker Jesse Jackson "did little to arrest the Democrats’ continuing decline—if anything, their messages likely reinforced it and placed the country in even greater lock step with the conservative populism being preached by Ronald Reagan and the Republican Party."

Mr. Cohen explain that he focused exclusively on speeches made during presidential campaigns because it is "a primal, competitive meeting place where great ideas stirring national rhetoric and aspirations for the future are fervently debated, dissected and discussed." That sounds more like a town hall meeting (or even a blog) than a campaign speech. But Mr. Cohen has correctly latched onto speeches as the prime portal through which to view, understand and appreciate what presidential hopefuls have in mind.

And he even tries to give us an idea of what it must have been like to hear the speeches being delivered.

About Barry Goldwater’s 1964 wake-up call to conservatives in the Grand Old Party, Mr. Cohen writes that "in the audio of the speech, Goldwater’s tone belied the insistence of his language. His monotone delivery makes it hard to believe that Goldwater was truly convinced he could win in November."

But then the candidate gets going, inflamed by the pure ideology of conservatism, and his language "practically crackles off the page."

Goldwater lost, too.