There was a time, not quite within the memory of Americans now alive, when the principal argument between the major parties was over the tariff. Democrats wanted a low one, Republicans a high one.
There were differences between the parties, but chiefly they were in perception. Democrats were a more raffish crowd. They were said to enjoy themselves more. On matters of patriotism, they were distrusted by Republicans, who had almost begun political life by "waving the bloody shirt" at Democrats for being sympathetic to the Confederate cause.
That preceding paragraph, portions of which I co-wrote with my reporting partner, James Perry, a quarter-century ago, once was true, but seems not so much quaint as antiquarian today.
Woodrow Wilson began the change, Franklin Roosevelt fueled it, Richard Nixon accelerated it, and Ronald Reagan clinched the transition. The charge that there's "not a dime's worth of difference" between the two parties -- George Wallace's proclamation in 1968 when he ran against both of them -- now also seems antiquarian, though nothing about the Wallace of that period ever will seem quaint.
The two parties today are perhaps more different than they have been since the Civil War and the end of reverberations over Reconstruction.
They've swapped positions on the tariff -- Democrats now want a high one and Republicans generally believe that higher tariffs mean lower productivity -- and they differ about almost everything else.
One party generally believes in abortion rights, the other does not. One party would permit taxes to rise, the other would not. Though both believe the nation is nearing a dangerous cliff on Social Security and Medicare, their prescriptions for avoiding the entitlements disaster are so different as to be irreconcilable -- as we have seen.
They also differ in geography. The South is solid again, but today's Solid South is a deep Republican red. It used to be a Democratic blue -- as blue and as seemingly permanent as the sky, even viewed from the perspective of a pack of yellow dogs. The fact that almost none of the readers of this column ever has heard the phrase "yellow dog" in conversation seals my point.
This used to be a country of partisan contention but often of policy consensus. This was true as recently as 1960, when the two candidates, Vice President Nixon and Sen. John Kennedy, bickered a lot but differed little.
In that year, Clinton Rossiter, a Cornell University political historian, wrote: "There is and can be no real difference between the Democrats and the Republicans, because the unwritten laws of American politics demand that the parties overlap substantially in principle, policy, character, appeal, and purpose -- or cease to be parties with any hope of winning a national election."
Mr. Rossiter died in 1970, as cracks in the world he knew were becoming evident. Mr. Nixon's Southern Strategy left the yellow dog mortally ill; Mr. Reagan killed it. It was in large measure race, which had created the differences between the parties in the 19th century, that rendered the parties different as the last century ended and the new one deepened.
First, the Democrats became the party of civil rights. Then the Republicans became the party of patriotism, small government, and social conservatism. These wedges forced apart the foundations of the American party system.
Which brings us to Campaign 2012. A generation ago, it would have been inconceivable that one party would nominate an African-American and the other a Mormon -- and that both would have Catholic running mates. We're over that; all those things happened in one year.
We live in a different world, in which the phrase "yellow dog" demands to be defined. So before we close, a primer on this curious canine.
There are several etymological explanations for the term, but two will suffice: The notion that a Southerner would vote for a yellow dog before he would vote for a Republican, or the companion idea that a Southerner would vote for a yellow dog if he were the nominee of the Democratic Party.
The yellow dog is dead. Dead with it, alas, is the golden age of political metaphor. We may not all mourn the death of the former, but we can all grieve at the demise of the latter.
David Shribman is executive editor of the Pittsburgh Post-Gazette.
Contact him at: firstname.lastname@example.org