WASHINGTON — In 2016, Michelle Obama’s words became the Democrats’ defining creed to counter Donald J. Trump’s battering ram of a presidential campaign: “When they go low, we go high.”

Two years later, the appeal of “high” seems low.

As much as any policy tensions or messaging debate within the party, this question of tone — of how to combat Mr. Trump effectively without slipping into a pale imitation — is perhaps the central divide of this Democratic moment (and the next one, with the 2020 campaign looming).

How will Democrats choose to revise Mrs. Obama’s sentence, with Mr. Trump heaving insults from the White House and the rally stage — his pre-midterm bully pulpit?

“When they go low, we kick them,” Eric H. Holder Jr., the former Obama administration attorney general and a possible 2020 candidate, said this week.

“When they go low, I say hit back harder,” Michael Avenatti, the cable-ubiquitous lawyer flirting with his own presidential run as a Trump-style brawler, told a crowd in Iowa over the summer.

Few but Mrs. Obama seemed inclined to defend the original refrain. “Fear,” Mrs. Obama told NBC on Thursday, “is not a proper motivator. Hope wins out.”

But for many Democrats, it does not seem to be winning out, at least for now.

It is one thing for Mr. Avenatti, the telegenic anti-Trump id, to seize this kind of rhetorical real estate. But increasingly, much of the Democratic establishment seems to be marching that way, too, channeling the righteous anger of the progressive base.

“You cannot be civil with a political party that wants to destroy what you stand for,” Hillary Clinton told CNN this week. “If we are fortunate enough to win back the House and/or the Senate, that’s when civility can start again. But until then, the only thing that the Republicans seem to recognize and respect is strength.”

Mrs. Clinton seems unlikely to recommend her 2016 campaign slogan, “Stronger Together,” to the next generation. Yet if she failed to reflect the national mood during her last run, Democrats had spent years before that straining to project indignation in the right proportions.

Former President Barack Obama could seem removed, ever mindful of the minefields underfoot for a black politician emitting fury.

Mrs. Clinton, before her 2016 turn as a stateswoman and grandmother, staked her 2008 bid on evincing a toughness that could match any man’s.

Former Vice President Joseph R. Biden Jr. has held himself out as a Democratic rarity: unwilling to give up on the white working-class voters who lifted Mr. Trump, but unafraid to go nose to nose with their president.

The result: down-home paeans to a well-placed whupping.