Oratory just isn’t what it used to be. It never is. Winston Churchill’s reputation as an orator has proved lasting but is very much a post1940 creation. Many of his inter-war contemporaries thought him a laborious speaker who suffered by comparison with Gladstone’s moral intensity and Disraeli’s foppish glitter. And those Victorian titans, in their time, were clearly not a patch on the polished prose and poised delivery of Edmund Burke and Charles James Fox a century earlier. Oratory’s greatest artists tend to be dead before they are recognised, and their epoch, like any golden age, reproaches those who come afterwards.

Barack Obama bucks that trend, since it is the quality of his speeches – and some nifty campaigning on the internet – that has elevated the president-elect to greatness. Many of his devices – the repetition of the same phrase at the beginning of successive sentences, for instance – would have been familiar to Cicero. But the sweep of Obama’s words is entirely of its time, involving his audience in a narrative that seems, at first sight, highly personal.

The repetition of “Yes, we can” is a choreography borrowed from those Protestant churches whose congregations punctuate the sermon with encouraging remarks that echo the preacher’s own. Obama’s central theme is his representative self, and his experiences as “the son of a black man from Kenya and a white woman from Kansas” are central to his oratory. But the way he shares that autobiography with his listeners makes it seem emblematic of an inclusive America rather than just one individual’s life story.

Flattery is at work here too. Obama is gracious to his listeners and assumes that he doesn’t need to spell out his speeches’ internal allusions to the themes and phrases of Lincoln and FDR, of JFK and Martin Luther King. These are the chosen forebears connecting Obama to his audience in an implicit bond and through words that don’t need obtrusive quotation marks. Having made that lineage his own and declared himself to be its heir, he practically disappears from view as a fallible politician who might be pinned down and interrogated. This is the Holy Spirit of American politics: a salvationist figure who seems to be everywhere and yet, frustratingly, nowhere when it’s time to define.

British attitudes to oratory reflect changing times. Pollsters suggest that being asked to speak in public is right at the top of most people’s phobias, along with spiders, snakes and heights. Those who like doing it are a very small minority, and a career choice involving prolonged bursts of speechifying seems eccentric to most.

Actors’ performances on the English stage reflect a new trend in favour of mumbled and sometimes inaudible speech, a reflection perhaps of the suspicion that diction that is too perfect lacks the human touch. Nonetheless, admiration at a task well executed explains the high fees commanded by some expert practitioners of the public speaker’s art, such as William Hague. The politician, though, who enters into that line of work is employed as an entertainer. Adroit timing and well-judged nuance are required to hold attention, but for the after-dinner audience it’s the joke and the anecdote, not the policy option, that justifies the fee.

The considered and lengthy political speech survives by the skin of its teeth in parliament, and is dusted down for more public display during the party conference season. Beyond these arenas it has faded from sight, and attention must now be gained by pithier means. No politician in his right mind would buttress his position by using a quotation from Greek and Latin authors as Harold Macmillan used to do. Boris Johnson still flies the flag for these literae humaniores, but more in the form of the diverting tag than as a basis for argument.

That British Christianity is in such decline makes for an important political difference between us and the US. Listening to an argument expounded in a sermon was once the shared experience of millions in this country, and it therefore seemed unsurprising that politicians as well as clergy should demand the best part of an hour to get their points across. Such physical endurance now seems extreme, but there’s an overall loss of literary power also involved. The biblical imagery that is such a lively presence in the American political speech has dropped out of our culture and has not been replaced by any equivalent source of poetic power.

The glancing one-liner that can pierce on impact shows that oratory lives on in British politics – as in Vince Cable’s reference to Gordon Brown as “Mr Bean”. The literary style may owe more to stand-up than it does to Cicero, but the deftness of touch shows that good rhetoric can adapt to the times and deliver its blows.

Nor should we weep for some imagined past in which most British politicians were as eloquent as Demosthenes. History can be appropriately dismissive of some orators who were thought great in their day. Michael Foot’s speeches were once considered an example of parliamentary oratory at its most sublime, but read in cold print they now seem merely argumentative rather than well argued. And a speech that is really consequential in historical terms need not be well delivered. Margaret Thatcher was an indifferent public speaker and all that voice training only made matters worse. But her Bruges speech on Britain’s relations with the European Union acquired oratorical significance because its words and arguments had an undeniable impact on the course of events.

Tony Blair’s often verbless sentences in his early speeches as prime minister were a much-parodied feature of the new Labour movement. Though so criticised, they also developed rhetoric a stage further by directing it towards a new audience – one intolerant of long-winded delivery and stale parliamentary conventions. The style suited the 1990s, a time when Britain’s political parties had converged on economic policy. Rhetorical fireworks were then a spectacle to amuse rather than a debate of consequence.

The arrival of a division between tax-and-spend Labour and the debt-averse Tories marks the beginning of a new phase in the history of British oratory. Gordon Brown retreats to the Keynesian comfort zone while David Cameron veers to the stern, unbending Toryism of old. These are real differences and their crystallisation will need all the powers of oratory at the party leaders’ command.

In Our Time: The Speeches that Shaped the Modern World, by Hywel Williams, is published by Quercus on Thursday

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president