But even that misses the bigger point. What Democrats can least afford in the 2016 campaign is a deep fissure between moderate and progressive wings. It doesn't matter whether the challenger to Clinton is Warren, or Virginia's former senator Jim Webb, who has formed an exploratory committee, or even Vermont's charming socialist Bernie Sanders. If Clinton is pulled too far to the left in primary battles, it will damage her chances in the general election.

Substitute "right" for "left" and you have what, among other things, undid Mitt Romney in 2012. The vexing problem for the GOP is that the ultra-conservative wing has enough clout to influence many state primaries, but not enough juice to win a national election. Romney staked out positions in early debates that worked against him in the final run.

Brooks writes: "The emotional register of the Democratic Party is growing more combative. There's an underlying and sometimes vituperative sense of frustration toward President Obama, and especially his supposed inability to go to the mat."

Translated into terms Republican bulldogs like Karl Rove might favor: If Democrats triangulate, with moderates such as Clinton defending herself against progressives like Warren, while each takes shots at the Obama Administration, the election is wide open.

That's essentially what happened to Democrats in 2000, when consumer advocate Ralph Nader – staking out wild progressive positions like universal healthcare! – ran as a third party candidate. He got 2.7 percent of the vote and a margin in Florida that probably cost the election for Democrat Al Gore.

Since then, the sheer volume of primary debates, the ever-lengthening campaign, and 24/7 media scrutiny have made it easier for extremist spoilers to be influential within the two-party structure.

As for the Republicans, when I last visited the subject 10 months ago I wrote that Jeb Bush looked like the frontrunner. Now, he's announced that he will "actively explore" making a run.

Oddly, a Bush candidacy could help Hillary Clinton. Among her negatives is the fact that Americans don't really like family dynasties in high offices. Any Republican other than Bush could play that card, but the brother of one president and son of another certainly could not.

If Bush jumps in, he'll face much of the same Tea Party opposition that hampered Mitt Romney. He'll confront a dozen opponents in debates and will find himself attacked by his own party for questionable financial dealings, just like Romney. If he wins the nomination, he'll be badly bruised.

All that, too, would be good for a Clinton candidacy. Unless, of course, someone like Elizabeth Warren throws a monkey wrench in the process.

What Democrats have to fear most in 2016 are Democrats themselves.

(c) Peter Funt. This column was originally distributed by the Cagle Syndicate.