Heading into Sunday's Democratic presidential debate, Sen. Bernie Sanders of Vermont is catching up to Hillary Clinton. (AP Photo/Nati Harnik)

Before the last Democratic primary debate, on the Saturday before Christmas, I wrote that the weekend scheduling was “very friendly to Hillary Clinton.” Viewership seemed sure to be low (it was), which limited the opportunity for upstart Sen. Bernie Sanders of Vermont to impress voters and make a move.

The Sanders camp even suggested that the Democratic National Committee’s decision to stage three consecutive weekend debates leading up to the start of primary voting was part of a calculated strategy to insulate the front-running Clinton, who at the time held a commanding lead in national polls: 25.1 points, according to the RealClearPolitics average.

Now, with Clinton and Sanders (and former Maryland governor Martin O’Malley) set to meet again Sunday night in Charleston on NBC, I’ve changed my mind. In my defense, it's because the circumstances have changed -- big time.

This time, a schedule that appears likely to produce another low rating — capping a week of political overload that already has featured the State of the Union address and a Republican debate — could actually work against Clinton.

In less than a month, the former secretary of state has lost two-thirds of her national lead; it’s down to 8.6 points and is falling faster than it did in 2008, when Clinton blew a sizable advantage over then-Sen. Barack Obama of Illinois.

In the critical, early-voting states of Iowa and New Hampshire, Clinton and Sanders are virtually tied. The media narrative at the moment is that Clinton is in trouble.

You know what she could use right now to regain her grip on the race? A dominant, stop-all-the-nonsense performance in front of a big debate audience. All of a sudden it is Clinton -- not Sanders -- who needs to change the momentum. She’s no longer in a position in which preserving the status quo is good enough.

Clinton could very well make a terrific showing on Sunday night. She probably will, actually. She’s been the strongest debater in the first three meetings, and I imagine she’ll be even more prepared than usual, knowing the stakes.

But it won’t do her much good if no one watches. The prospect of low viewership, which seemed so beneficial a short time ago, now looks like a real drawback.

And if Clinton is dominant, how much will it be covered -- or even read about -- over a long holiday weekend?