PHOENIX (NYTIMES) - As the candidates for chairman of the Democratic National Committee gathered here for a forum on Saturday, they wrestled with a vexing question: How to confront the asymmetrical political warfare of President-elect Donald Trump.

Be strategic, the candidates advised, and do not take him up on every feud.

"If you try to go tweet-to-tweet with him, more often than not you're not going to succeed," said Thomas E. Perez, the secretary of labor, warning about going to "a knife fight with a spoon".

Sally Boynton Brown, executive director of the Idaho Democratic Party, invoked what she called "Psychology 101" for narcissists.

Every response to Trump's provocations, she warned, risks helping him "grow more powerful".

And Pete Buttigieg, the mayor of South Bend, Indiana, said simply, "We're going to need to be smarter than just talking about how bad he is."

Yet just as the would-be leaders of the Democratic committee, who were assembled for the first of four officially sanctioned candidate forums, preached prudence and calculation in the Trump era, others in the party were responding with fury to the president-elect's latest Twitter outburst.

Trump's ridicule of Rep. John Lewis of Georgia as being "all talk" set off outrage among Democrats, with many defending their colleague, some vowing to join him in boycotting the presidential inauguration and most determined to make Trump pay a price for taking on a giant of the civil rights movement.

Lewis had said a day before that Trump was not a "legitimate president".

The president-elect's willingness to attack seemingly any and all comers - Lewis is one of the few figures revered across party lines - nearly every day makes him an even more difficult target for Democrats.

Less than a week before Trump is sworn in, there is a widening disconnect among Democrats over how to challenge a leader whose talent for stirring controversy can blur, rather than sharpen, the lines of attack against him.

Democrats, here and in Washington, say it is folly to engage him on his preferred terrain of insults and bombast.

They suggest that one of Hillary Clinton's mistakes was to try to isolate him from the Republican Party by portraying him as an aberrant figure.

The more effective course, Democrats say, is to focus on policy and assail Trump for not living up to his populist promises as he installs a largely wealthy Cabinet and begins rolling back the Affordable Care Act.

"I think it's a dangerous game to chase every new outrage," said Sen. Brian Schatz of Hawaii, a new member of his party's leadership.

"We're going to have to make the case that voters were sold a bill of goods and this is a hard-right president and hard-right Congress."

The party cannot, Schatz added, "get distracted by the latest shiny object".

Democrats, however, seem to have trouble following their own advice.

While most leading Democrats would prefer, for example, to highlight how many Americans would lose their insurance coverage if Republicans repeal the Affordable Care Act, they cannot turn away when Trump attacks the intelligence agencies or the family of a fallen soldier.

Or, especially, when he takes aim at an esteemed figure like Lewis.

Trump's willingness to dynamite political norms, whether with his incendiary statements or with his disregard for traditions like releasing tax returns or divesting assets, is creating an irresistible temptation for the opposition to veer away from more conventional attacks on issues.

Regardless of how deft Democrats are at prosecuting the case against Trump, his tendency to let loose invective the way other politicians churn out news releases could potentially be his undoing as president.

His approval rating is below 40 percent in some surveys, a historically low figure for an incoming president that means he will effectively enter office in crisis.

But, despite all predictions in the Republican primary contests and then in the general election, Trump's succession of perceived missteps never proved fatal.

It turned out that waiting for his inevitable collapse based on his behavior amounted to a grave miscalculation of what the electorate cared most about.

"Jobs and wages are more important than anything to do with process," said Sen. Michael Bennet, D-Colo.

But he acknowledged that it was becoming increasingly difficult to keep a sustained focus on high-fiber topics when the controversy of the hour garners so much attention.

"One of the things that I worry about is that we've reached a point in our politics, and frankly in our journalism as well, where we've sort of turned it all into a reality TV show," he said.

In interviews here in Phoenix, Democrats voiced a determination to resist the spectacle - to not play by Trump's rules.

"We can complain all day about every stupid tweet, but the bottom line is that's not going to change anything," said Mitch Ceasar, a member of the Democratic committee from Florida who is running for a vice chairman post.

"We have to have precision and be narrow in our scope."

Yet just minutes after Ceasar offered his advice here, his party seemed to be responding to what it surely considered a "stupid tweet."

As she took the stage to begin the candidate forum, Donna Brazile, the interim party chairwoman, said the event could not begin before she offered comments about the "tweets of a certain president-elect".

Brazile won a standing ovation from the Democratic audience for her denunciation of Trump's attack on Lewis.