The Associated Press / Former Vice President Joe Biden, left, is happy to stand quietly as the current poll leader while U.S. Sen. Bernie Sanders, I-Vermont, rattles on during Thursday's Democratic presidential primary debate.

If the impeachment of President Donald Trump had been top of mind for most Americans, Thursday night's Democratic primary debate might have been expected to have a wide audience curious about which of some two dozen candidates might be the most suitable to replace the president.

However, ratings have fallen in each of the party's six debates, and Thursday's was no exception. Voters are either sticking with what they've got, know for which contender they'll vote or just don't care.

Or perhaps they were wrapping Christmas presents and watching a Hallmark movie.

But that's perfect for former Vice President Joe Biden, who remains the Democrats' polling leader for the nomination. With less than two months until the first state has its say, the front-runner status is his to lose. So, prone to gaffes (the most recent a bizarre story he told earlier this month about children rubbing his leg hair and "jumping on my lap"), the less he has to say, the better.

For the first 45 minutes of the debate, he was sixth out of the seven candidates in speaking time with just over three minutes. He wound up fifth out of the seven candidates, with a full four minutes less than Sens. Bernie Sanders, I-Vermont, Amy Klobuchar, D-Minnesota, Elizabeth Warren, D-Massachusetts, and South Bend, Indiana, Mayor Pete Buttigieg.

(Read more: Key takeaways from Democratic presidential debate in L.A. [video])

Thus, he could only stand back and grin as Warren, Klobuchar and Buttigieg duked it out. An exchange between Warren and Buttigieg became particularly tense after Buttigieg — hoping to appeal to less extreme voters — said he was "the only person on this stage that is not a millionaire or billionaire."

Warren, attempting to fight back after her campaign stalled following last month's debate when she had trouble explaining the costs of some of her promises, accused the South Bend mayor of holding a California fundraiser in a "wine cave full of crystals," where participants could pay $2,800 to dine with him.

"Billionaires in wine caves should not pick the next president of the United States," she said.

Klobuchar said she "did not come here to listen to this argument. I came here to make a case for progress. And I have never even been to a wine cave."

The Minnesota senator, desperate to grasp a rung in Iowa's first-in-the-nation caucus, where Buttigieg leads the polling, wasn't through with the young mayor.

"When we were in the last debate, mayor, you basically mocked the hundred years of experience on the stage," she said. "While you can dismiss committee hearings, I think this experience works. And I have not denigrated your experience as a local official. I have been one."

Klobuchar also referenced Buttigieg's one failed attempt at running for statewide office.

"[If] you had won in Indiana, that would be one thing," she said. "You tried, and you lost by 20 points."

It was, national pundits thought, Buttigieg's worst debate to date.

Meanwhile, the candidates wrestled with guilt over the fact no black or Hispanic candidate qualified for the debate. Entrepreneur Andrew Yang, the only nonwhite candidate present, argued that happened because blacks and Hispanics have less disposable income to donate to candidates.

Then, one might wonder, how does one explain Barack Obama? Or the fact Biden has so much black support he is leading the polling in South Carolina?

So while Yang whiffed on one question, he might have been the only one on the stage who understood why Trump appealed to many voters in 2016 and why support for the president's impeachment dropped as impeachment hearings went on this month.

"If you turn on cable network news today," he said, "you would think he's president because of some combination of Russia, racism, Facebook, Hillary Clinton, and emails all mixed together. But Americans around the country know different. ... The more we act like Donald Trump is the cause of all of our problems, we lose trust that we can actually see what is going on in our communities and solve those problems."

(Read more: AP FACT CHECK: Examining claims from 2020 Democratic debate)

He wouldn't say it, but Americans have seen through the impeachment pursuit. They recognize the politics of it for what it is. But if they like Trump, they're not ready to throw him over for a few words in a phone call with a foreign leader who never felt any pressure in the call himself.

"What we have to do is ... stop being obsessed over impeachment, which unfortunately strikes many Americans like a ballgame where you know what the score is going to be," Yang said, "and start actually digging in and solving the problems that got Donald Trump elected in the first place."

Unfortunately for Democrats, too many people think the guy they elected in 2016 is already solving those problems, and they haven't seen anyone with whom they'd rather replace him.