The Times piece was published in August, months after Bush's opponent, John Kerry, had already worked the phrase into his regular rotation. And that was just in the general election. In the primary, a spokesperson for Kerry's eventual running mate, John Edwards, told the Des Moines Register that "this remains a tight race because Iowans realize this is the most important election of our lifetime." Edwards lost that close race to Kerry.
The most recent iteration of the phrase came at the Democratic convention on Wednesday night. "This is the most important election of our lifetime," director Lee Daniels told the assembled delegates, to applause. No one at the Republican convention seems to have said it, in keeping with Donald Trump's promise to run a different sort of campaign.
The earliest usage by the New York Times is older: A reference to an election in Pennsylvania from October 1856. "The most exciting, and it is by all parties conceded the most important election that has been held since the organization of our Government, takes place to-day in Pennsylvania," the article reads. This was the election of Pennsylvania's House delegation and, while it may have been the most important election in the first 67 years of the country, it hasn't really held up.
If you dip into the archive of news stories at Nexis, the first time the expression is used is by Nancy Reagan in 1980. "This is the most important election of my life," she said. "The outcome will affect the nation and the world." That last part, at least, was clearly true.
Reagan's use was unusual in that it came from the winning side. Often the exhortation comes specifically because the candidate or his proxy needs to remind flagging supporters that they simply had to go to the polls. Walter Mondale to supporters in 1984 ("This is the most important election of our lives. This is a race we can't afford to lose."). Ralph Reed at a meeting of the religious right in 1996 ("As you and I gather on the threshold of the most important election of our lifetime, we can truly say we have been brought into the Kingdom for such a time as this."). The chair of the DNC in 2000 ("It's certainly the most important election of my lifetime."). It's a slightly longer way of saying, "people, please."
It also takes advantage of one of the quirks of human psychology: immediacy. Nothing is ever more important than what's happening in the moment, both because past emotional peaks fade and because the present is the moment you can affect. Sure, we know the invasion of Normandy was big what with the liberation of Europe and all that, but we can't actually do anything about it. As a call to future action, history isn't that great.
There's also the fact that the present always feels unique -- and in this election, it is. The election of 2012 felt starkly different from the election of 2008 while it was happening, but now that distinction seems like noticing that the church ice cream social had chocolate last year and vanilla this. Relative to the 2008 and 2012 elections, 2016 isn't an ice cream social with a new flavor, it's an NHL game on Jupiter played by mathematical concepts. It may not be the most important election of our lives, but -- so far at least and relative to my life -- it's the weirdest.
In other words, sometimes an election actually is the most important of your life. Happens at least once. President Obama's speech that followed Lee Daniels' on Wednesday night tried to tap into that. You can think of it as simply a longer way of his arguing: This time, America, the election really is that important. This time, America, there really is a wolf.