The paradox of the last week is this: The fortunes of Republican presidential candidate John McCain have been rising, while the fortunes of the Republican candidates, overall, have been falling. So what gives? Is McCain destined to win a lonely victory at the political pinnacle, while other Republicans sink further into minority status in lesser competitions? The answer, to be blunt about it, is probably “yes.”

And why will we see “two tier” election results in 2008?

One obvious reason is the fact that McCain is doing well; he has thrown Barack Obama onto the defensive, and he is now ahead in the latest polls. Meanwhile, the Republicans running for Congress have faced mostly bad news, including the recent indictment of Alaska Senator Ted Stevens. Just this morning we saw a long report from The New York Times, detailing the decline in Republican voter registration nationwide. Now admittedly, the Times is a liberal paper, but unless it is simply making up numbers, these data should be legitimately scary to Republicans: “In six states, including Iowa, New Hampshire and Pennsylvania, the Democratic piece of the registration pie grew more than three percentage points, while the Republican share declined.”

And so it’s hard to argue with the Times’ overall conclusion:

While the implications of the changing landscape for Mr. Obama and Mr. McCain are far from clear, voting experts say the registration numbers may signal the beginning of a move away from Republicans that could affect local, state and national politics over several election cycles. Already, there has been a sharp reversal for Republicans in many statehouses and governors’ mansions

OK, so those are some numbers. And politics, like baseball, is, after all, a numbers game. You study the statistics of the past to gain clues about the statistics of the future.

Now to the second reason: Americans like divided government.
How do I know? Because it’s been the pattern in post-war American politics. For 37 of the last 62 years, 1946-2008, the White House has been controlled by one party while at least one chamber of Congress has been controlled by the other party. Today, for example, it’s a Republican President, George W. Bush, in the White House and a “loyal opposition,” led by House Speaker Nancy Pelosi (D-Cal.) and Senate Majority Leader Harry Reid (D-Nev.), dominating the 110^th Congress.

And since WW 2, that’s been the most typical power distribution: For six of the eight years of his presidency, Republican President Dwight Eisenhower dealt with the Democrats who controlled the 84^th, 85^th, and 86^th Congresses. Later it was Republicans Richard Nixon, Gerald Ford, Ronald Reagan, and George H. W. Bush squaring off against Democrats who controlled one or both chambers, usually both.

Indeed, for 29 of the last 62 years, that’s been the most frequent pattern. Or, as statisticians would call it, “the modal score.” And for another eight years, in the 1940s and in the 1990s, it was Democratic presidents, Truman and Clinton, arrayed against Republican Congresses. Which is to say, 60 percent of the time over the last 62 years, control of the two popularly elected branches in Washington has been divided between the two parties.

For the record, Democrats controlled all the marbles in Washington—that is, both the White House and Congress—for a total of 18 years during this period (1949-1952, 1961-1968, 1977-1980, 1993-1994). And the Republicans owned both branches of government in 1953-1954, during much of 2001, and then, again, from 2003 to 2006.

So why this pattern? Why this divided control? Some suggest it’s a function of the voters’ collective mistrust of both parties: They simply don’t want to see one party control everything in Washington DC. But are the voters really that subtle in their thinking? Are they that willing to split their tickets, knowing that “gridlock” is the most likely outcome of such divided control? Well, the answer would seem be in the affirmative—it’s hard to argue with the historical record.

And in fact, polling surveys measuring trust in government tend to underscore the voters’ logic—when you don’t trust ‘em, divide their power. When trust in the federal government is high, voters seem happy to give one party the political equivalent of the football, so that the favored party can run with it for awhile. And yet when trust in the federal government declines, power is split. That’s been the case in the last decade. Trust and confidence in the federal government spiked after 9-11, reaching as high as 73 percent in 2002. But since then, various factors—most likely, frustration over Iraq, the response to Katrina—have caused trust in government to plummet, all the way down to 37 percent, according to the Pew Center. And so, in 2006, voters took control of Congress away from the incumbent party, the Republicans.

Democrats hoped that their triumphant 2006 election would be just an overture to an ever bigger win in 2008, but, as we have seen, that doesn’t seem to be shaping up. If the voters don’t want Republicans to have all the power in DC, maybe they don’t want Democrats to have all the power, either.

So the voters seem to be saying, “A partial pox on both your houses.” And yet since the Democrats seem solidly entrenched in Congress, for John McCain, that voter-wish becomes a blessing.