It is generally true to say that in order to be successful in politics, you have to be capable of conveying a sense of optimism about your country and its future.
One of Tony Blair's key strengths at the start of his leadership was his ability to communicate a vision of a bright 'New Britain' in contrast to the greyness of the John Major years.
Later, David Cameron donned the same mantle, exhorting the voters to "let sunshine win the day" as he pitched himself against a tired old Labour government.
But there can come a time when optimism crosses the line into mere boosterism, and in my view it’s a line Mr Cameron crossed in his party conference speech in Manchester this week.
"Let's reject the pessimism. Let's bring on the can-do optimism. Let's summon the energy and the appetite to fight for a better future for our country, Great Britain," he told the Tory faithful.
And again: "So let's see an optimistic future. Let's show the world some fight. Let's pull together, work together, and together lead Britain to better days."
If, by his own admission, Ed Miliband is no Tony Blair when it comes to speechmaking, then David Cameron is no Winston Churchill either.
And I sense that I was not the only one who was left somewhat unconvinced by the Prime Minister's attempts this week to summon up the bulldog spirit.
To take another of Mr Cameron's optimistic soundbites: "Right now we need to be energised, not paralysed by gloom and fear."
Yet in the eyes of many, it is his government which has produced the economic paralysis by cutting too far, too fast and choking off the fragile recovery that had begun to see us through the downturn.
In this context, the announcement of a mere 0.1pc growth in the economy during the last quarter could not have come at a worse time for Mr Cameron.
Against that gloomy backdrop, his attempts at uplift were no more persuasive than his earlier, now seemingly discarded mantra that "we're all in it together."
The most startling omission in Wednesday’s speech was the absence of any policy detail from the Prime Minister on how he plans to ensure that economic growth in the next quarter does not grind to a halt altogether.
“Here’s our growth plan,” he said. “Doing everything we can to help businesses start, grow, thrive, succeed. Where that means backing off, cutting regulation – back off, cut regulation. Where that means intervention, investment – intervene, invest. Whatever it takes to help our businesses take on the world – we’ll do it.”
Commenting on this passage on his blog, Alastair Campbell wrote: “What was happening in the Team Cameron speech meetings? Did nobody stop and say ‘er, Prime Minister, this is a bit embarrassing, and doesn’t really say anything?’”
Okay, so Campbell is hardly an objective observer - but he knows what it takes to produce a good conference speech, and he also knows a turkey when he sees one.
The background story bubbling away behind the scenes at this conference was the nascent leadership battle to succeed Mr Cameron.
Home Secretary Theresa May made her pitch for the affections of the Tory Right by inflating a somewhat tendentious story about an over-stayed student who defied deportation on the grounds of owning a cat into front page news.
Then, as always, there was Boris Johnson, the London Mayor lobbing his own hand-grenade into the Tories' never-ending debate about Europe by announcing he favours a referendum on EU membership.
And even Mr Cameron himself felt the need to acknowledge Chancellor George Osborne's leadership ambitions, jesting about his choice of The Man Who Would Be King as an audio book.
But joking aside, the Prime Minister should surely be deeply worried by this outbreak of posturing and positioning among the potential contenders for his crown.
The result of the last general election showed that the public are not entirely convinced by him, and I sense that his party are increasingly unconvinced by him too.
Do the Tories believe that Mr Sunshine’s unflagging sense of optimism will be enough to save them from the gathering economic and political storm clouds ahead?
Or are they already secretly planning for Life after Dave?