On Labor Day 2007, Mitt Romney and Barack Obama each spent the afternoon in the quintessential New Hampshire town of Milford as they worked to earn votes at a holiday parade.
Romney had reason to feel good that day about his chances of winning the Republican nomination, as he led in the polls in both Iowa and New Hampshire and appeared to have the financial resources to go the distance.
The former Massachusetts governor showed off his ebullient mood by jogging, rather than walking, the parade route on that late-summer afternoon, crisscrossing the street to shake hands and introduce himself to the voters who would cast their ballots in the first-in-the-nation primary four months later.
As his staff and members of the media struggled to keep up, Romney spotted a small crowd of people who had gathered under the cool shade of a tree just off the parade route.
Check out John Dickerson's "Hotsheet Live" Reporters Roundtable with Real Clear Politics and CBS News' Scott Conroy, USA Today's Susan Page and the New York Times' Jeff Zeleny in the video to the left.
Without hesitation, the candidate bounded past a cadre of visibly concerned Secret Service agents who had formed a loose circle around Barack Obama and approached the junior senator from Illinois, who was struggling to turn the tremendous enthusiasm behind his campaign into movement in the polls against Democratic front-runner Hillary Clinton.
With a burst of his now familiar staccato laugh, Romney shook Obama's hand as television cameramen jostled to get the shot.
The two candidates wished each other an amiable "good luck" with their respective campaigns and headed their separate ways.
As far as either side remembers, the only other time that the current president and the presumptive GOP nominee met face to face was when they each spoke at the 2004 Gridiron Club Dinner in Washington, D.C.
The fact that the two men competing for the nation's highest office have spent almost no time in each other's presence stands in contrast to the dynamic that existed four years ago. Then, Obama and Republican nominee John McCain squared off in the general election after having worked alongside each other in the Senate for three-and-a-half years.
The testy relationship between the two was first exposed in an open letter that the Arizona senator sent to his freshman colleague in February 2006; in it, McCain accused Obama of reneging on a private promise to push through lobbying reform legislation under bipartisan parameters.
"I understand how important the opportunity to lead your party's effort to exploit this issue must seem to a freshman Senator, and I hold no hard feelings over your earlier disingenuousness," McCain wrote in the letter that oozed with biting sarcasm and foreshadowed the personal animus that boiled over during their 2008 battle. "Again, I have been around long enough to appreciate that in politics the public interest isn't always a priority for every one of us. Good luck to you, Senator."
As Obama and Romney gear up for a general election campaign that is expected to be particularly negative, neither politician appears to have any strong feelings about his opponent on a human level, even though their personalities and perspectives could scarcely be more diametrically opposed.
The extent to which their backgrounds differ is perhaps best exemplified by their adolescent years.
The son of a wealthy auto executive and governor who still recalls fondly the day in high school when he beat out "another fella" for his wife-to-be's affections, Romney was once photographed in 1966 decrying Vietnam War protesters at Stanford University -- not far from the Haight-Ashbury district where many of his contemporaries were tuning in to the Grateful Dead and Jefferson Airplane.
Obama, by contrast, has admitted to using drugs during his teenage years while struggling to "find himself" in a single-parent, nomadic existence that had almost nothing in common with the placid, strait-laced suburban life that Romney inhabited at the same point in his life.
The president has at times veered close to revealing a mild disregard for Romney -- one akin to the snide contempt many members of his campaign team have been accused of harboring for their likely opponent.
Obama recently took some heat after drawing attention to Romney's use of the outdated word "marvelous" (a label Romney applied to Paul Ryan's proposed budget) and noted during a speech Wednesday in Ohio that he himself "wasn't born with a silver spoon" in his mouth.
But rather than suggesting a personal hostility, these comments have come across as political tactics designed to bolster the impression that Romney sometimes has difficulty in relating to everyday people.
For his part, the GOP's likely standard-bearer has for months tempered his criticism of the president by adding that Obama is a "nice guy" -- even when Romney is speaking to highly partisan crowds replete with people who largely believe otherwise.
According to aides who have spent significant time with Romney, the former Massachusetts governor has not revealed in private any disrespect or personal enmity for the man whose job he seeks, even though he believes emphatically that Obama is an ineffective leader who is in over his head.
But with more than six months of campaigning to go, there is plenty of time for political circumstances to take their toll on the personal dynamic between the two men, which for the time being remains undeveloped.
The candidates' paths are unlikely to cross before Oct. 3 in Denver, when they are slated to meet for just the third time in their lives at the first of three scheduled general election debates.
It is there that Obama and Romney are expected to demonstrate at least one trait that they have in common: formidable debating skills and an ability to rise to the occasion under immense pressure.