Once upon a time, the two parties' national conventions chose presidential nominees. Now, they are television shows that try to establish a narrative -- one that links the long-since-determined nominee's life story with the ongoing history of the nation, one that shows how this one man is perfectly positioned to lead America to a better future. The hope is that the nominee will get a bounce in the polls.

Last week, the two erstwhile communist superpowers were in the spotlight. Starting on Aug. 8, China staged the Olympics -- an event on the schedule for years. Also on Aug. 8, Russia invaded the independent republic of Georgia -- which apparently caught our government flatfooted.

To understand changes in the political map, we naturally tend to look for contemporary explanations. But American political alignments are not written on an empty slate. Beginnings matter, and the civic personalities of states tend to reflect the cultural folkways of their first settlers.

Just when you think you've got the presidential race figured out, something comes along to upend your carefully wrought conclusions.

Sometimes public opinion doesn't flow smoothly; it shifts sharply when a tipping point is reached. Case in point: gas prices. $3 a gallon gas didn't change anybody's mind about energy issues. $4 a gallon gas did.

Looking back over the last 40 years, the presidential campaign that most closely resembles this year's is the contest between Gerald Ford and Jimmy Carter in 1976. The Republicans were the incumbent presidential party that year, as they are now, but the Democrats had a big advantage in party identification -- on the order of 49 percent to 26 percent then, far more than today.

Sixty years ago this month, the top story in campaign year 1948 was not the big poll lead of Republican nominee Thomas Dewey or the plight of President Harry Truman. It was the Berlin airlift.

"They're going to try to make you afraid of me," Barack Obama told the audience at a Jacksonville fundraiser last month. "He's young and inexperienced and he's got a funny name. And did I mention he's black?" Obama was doing here by inference what many of his supporters do more explicitly.

"Not Exactly a Crime" is the title of a book on America's vice presidents published in 1972 -- a year before Vice President Spiro Agnew was forced to resign for actually committing a crime.

As we enter the second half of the campaign year, facts are undermining the Democratic narrative that has dominated our politics since about the time Hurricane Katrina rolled into the Gulf coast -- most importantly, the facts about Iraq.