The last time we looked — wasn’t it just about five minutes ago? — the Democrats were in as commanding a position as they have been in a generation. A popular president. Huge majorities in the House and Senate. All the issues going their way. Plus an unusually low barrier for success — produce an economy that isn’t a catastrophe and don’t look, sound or smell remotely like George W. Bush.

So why are the newspapers, Web sites and airwaves full of talk of Democratic strains, Democratic breakdowns, Democratic fissures, Democratic tensions?

At the heart of all these conversations — at the center of the party handwringing — is a species of political animal called the Blue Dog, a beast that does not occur in nature but that, it turns out, occurs naturally in politics. If you understand the Blue Dog phenomenon, you may understand the Democrats’ problem — and you may conclude that the party’s difficulties aren’t new.

History lesson

In the old days, when Americans took civics, and took civic life seriously, every schoolboy and schoolgirl knew what a yellow dog was. The phrase, which almost certainly came from Alabama more than three-quarters of a century ago, grew out of the notion that some Southerners would (gladly) vote for a yellow dog if he ran on the Democratic ticket. In short: A yellow dog was a party loyalist.

Today’s Blue Dogs don’t look quite so loyal. There are, by last count, 52 of them, and they are fiscal conservatives within a party that hasn’t always preached, and seldom practiced, fiscal conservatism. They think of themselves as centrists, and given the broad range of ideology in the United States that exists today in comparison to decades past, that’s a pretty fair estimation.

But, in recent weeks, these Blue Dogs have been angry, snarling canines, slowing down the procession of health-care overhaul from a presidential candidate’s promise to a president’s signature. They have worked to cut the cost of health care and avoid new taxes to pay for expanding coverage to the uninsured. They have been successful, as these elements now are regarded as touchstones of the health plan that is being debated in coast-to-coast town meetings during the August congressional recess.

The concessions House leaders made to the Blue Dogs were not insubstantial. The politics of the House is ultimately the politics of numbers. There are more liberals than Blue Dogs in the Democratic caucus, and many of them worry that the new health-care system is beginning to look a lot like the old health-care system. Thus this August of agony for Democrats.

Wagging the dog

The Blue Dogs have become the tail that wags the Democratic dog. This is a pretty strong tail, for Democratic leaders have reluctantly come to recognize that the size of this group is what consolidated the Democrats’ power in November and is what contributes to the Democratic leadership’s influence today.

Big irony: Many of these lawmakers who so irritate the leadership and the Obama administration were the very people that White House Chief of Staff Rahm Emanuel, who in his last job knew that the Democrats couldn’t take power as liberals alone, personally recruited into congressional races. The fact that there are 52 Blue Dogs tells us that the Democratic Party is big enough to have 52 quasi-dissenters.

It may be hard to hold a broad party together, but — as the Republicans can tell you — it is far harder to make a narrow party a majority. That is the nature of our political system. American parties can’t get big without getting complicated. American parties can’t have power without having conflicts. American parties cannot rule without having contradictions.

Two of the most productive periods of Democratic rule were the high tides that gave the Democrats their New Deal and Great Society in the 1930s and 1960s. Both were times when the Democratic coalition included large numbers of conservative Southerners who made a mockery of the notion of Democratic unity on social issues.

Today’s Democratic dilemma is a modern-day equivalent — a quarter of the Blue Dogs are from states that were part of the Old Confederacy. They make it difficult for House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid to get their way — which is precisely their goal. Indeed, among some Blue Dogs that is a point of honor. The more they can be seen as tormenters of Pelosi, the stronger their support at home becomes.

The dissenters have always been with the Democrats, even in the glory years.

LBJ parallel

Senate Majority Leader Lyndon B. Johnson watched Sen. James Eastland, the Mississippi Democrat who headed the Judiciary Committee, and Sen. Richard B. Russell, the Georgia Democrat who was like a father to him, butcher the 1957 Civil Rights Act that he so wanted in order to prove that he was a national leader, not a regional figure and old-school Senate potentate. President Lyndon B. Johnson then watched the two men oppose the 1964 Civil Rights Act, which was supported by only one Southern senator, Ralph Yarborough of Texas.

Just as Johnson had his Southern Democrats, President Barack Obama has his Blue Dogs. Both dissenting groups specialized in biting their leaders in the toes, or elsewhere. But remember this: Russell’s 1964 civil rights filibuster was beaten back, allowing Senate Majority Leader Mike Mansfield of Montana to move for final passage of the legislation and Johnson to sign it. In the end, Russell delayed but did not destroy his president’s landmark legislation.