Democratic presidential candidate Elizabeth Warren speaks during the South Carolina Democratic Convention, Saturday, June 22, 2019 in Columbia, S.C.. (AP Photo/Meg Kinnard)

NEW YORK (AP) — The unwritten rules that have so far prevented the Democratic presidential contest from devolving into all-out conflict are about to be tested.

The early front-runner, former Vice President Joe Biden, has so far fended off the relatively gentle wrath of his rivals. The shortcomings of his most ambitious opponents like Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren have been largely overshadowed. And the fiery concerns of lesser-known candidates, such as former Maryland Rep. John Delaney and entrepreneur Andrew Yang, have been all but ignored.

That dynamic now changes as Democrats enter the most consequential week of the young 2020 campaign season.

Ahead of a major fundraising deadline, the candidates will face each other on the debate stage for the first time on Wednesday and Thursday. The clash serves as a microcosm for broader questions looming over the field, one chief among them: Should candidates attack each other more aggressively or focus their fire on President Donald Trump?

There are no easy answers for candidates desperate for a break-out moment.

In an interview, Democratic National Committee Chairman Tom Perez downplayed simmering tensions between two sharply divided wings of the party. One demands bold action on health care and climate change, while calling for Trump’s impeachment; the other favors a more pragmatic progressivism that confronts the same policy challenges with a bipartisan approach.

“What we do have is unity of values,” Perez said, noting that virtually every Democrat seeking the presidency supports universal health care coverage, combating climate change and civil rights.

Indeed, no one expects the escalation that lies ahead for Democrats to sink to the level of the Republican presidential debates in 2016, which were plagued by deeply personal attacks that have come to define the GOP’s take-no-prisoners approach in the age of Trump.

Privately, the better-known Democratic candidates concede that an overly aggressive posture could backfire at this early stage. It’s also unclear, in such a crowded contest, who would benefit should Biden or another top-tier candidate fall several months before the first primary votes are cast.

“We’re all going to focus on the issues,” Perez said when asked about the debates. “We’re not going to be talking about hand size,” a reference to GOP personal attacks from 2016.

Underlying the calculus is a real concern among party leaders, donors and strategists that Democratic infighting could threaten their chief goal: beating Trump.

But the lesser-known candidates cannot afford to be cautious. And for the first time, they will have the opportunity to voice their concerns on prime-time television facing their opponents.

“I’m offering real solutions and a lot of people in the race are offering impossible promises,” said Delaney, a pragmatic former Maryland congressman who has been actively running for president for nearly a year with little national fanfare.

Allies of more liberal and better-known candidates, including Warren, are concerned that Delaney in particular will play into Republican hands by savaging their prescription for health care — a universal health care plan referred to as Medicare for All — on national television. Delaney said he would not shy away from his criticism of the plan, particularly his contention that it would outlaw private insurance.

Another moderate Democrat, former Colorado Gov. John Hickenlooper, is expected to echo a popular Republican talking point by highlighting his Democratic competitors’ embrace of socialism. The business-minded Democrat has levied the same charge in recent weeks, but this time, he would be doing it on national television alongside Sanders, a self-described democratic socialist.

Unlike some of his competitors, Sanders has not held mock debates to prepare for the upcoming faceoff, according to senior adviser Jeff Weaver, who described such preparations as an “inefficient use of time” in such a crowded field, especially given Sanders’ experience on the debate stage in 2016. The Vermont senator has focused instead on studying written materials and preparing more succinct answers to accommodate the limited speaking time available to each candidate.