Wow...the U.S. really is undergoing a political shift!

Last summer, pollster Mark Penn found that just 32 percent of voters called themselves Democrats, which led Penn to conclude that, at least on the party-ID issue, "the Democratic party is currently in its weakest position since the dawn of the New Deal."

Now a new study by the Pew Research Center pegs the Democratic number at 31 percent, versus 30 percent who call themselves Republicans.

That's very bad news - if you're a Democrat - but what does it actually mean?