THE INCREDIBLE SHRINKING PARTY…. Chris Cillizza argued yesterday that the most important number in the latest Washington Post/ABC News poll wasn’t 69% (the president’s approval rating), 50% (the number of Americans who believe the country is going in the right direction), but rather, was 21%.

That’s the percent of people in the Post/ABC survey who identified themselves as Republicans, down from 25 percent in a late March poll and at the lowest ebb in this poll since the fall of 1983(!).

In that same poll, 35 percent self-identified as Democrats and 38 percent called them Independents.

These numbers come on the heels of Steve Schmidt, former campaign manager for Arizona Sen. John McCain’s presidential bid, declaring the Republican party a “shrinking entity” last week — citing the decline of GOP numbers in the west, northeast and mountain west as evidence.

It’s not just this poll. The New York Times published a new poll today and found that only 20% of Americans identify themselves as Republicans, the lowest number in at least 17 years. (It may be longer, but the poll internals only go back to 1992.)

There was some talk in Republican circles recently that the GOP is finally “back in the saddle.” If that’s true, the horse is looking pretty small.

Cillizza added, “The number of people who see themselves as GOPers is on the decline even as those who remain within the party grow more and more conservative. That means that the loyal base of the party has an even larger voice in terms of the direction it heads even as more and more empirical evidence piles up that the elevation of voices like former vice president Dick Cheney does little to win over wavering Republicans or recruit Independents back to the GOP cause.”

Which brings us back to yesterday’s discussion about the party’s base refusing to allow the party to progress or adapt. Indeed, while the GOP would presumably be looking for new ways to expand its numbers, Republicans are apparently intent on doing the opposite.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.