President Trump’s reelection campaign won’t say whether it would use stolen information from hacks or other breaches, setting up a clash with Democratic rivals who have pledged to forgo such tactics and prompting some worry in Trump’s own party.

Trump campaign representatives did not respond to several inquiries this week seeking its policy on purloined material, nor did White House officials. Their silence has fueled concerns about the integrity of the 2020 election, which escalated after Trump’s personal attorney suggested that using stolen items might be appropriate.

The recent release of the report by special counsel Robert S. Mueller III has brought renewed attention to the threat of election-year hacks. Mueller’s 448-page report paints the most detailed portrait yet of Russian interference efforts in 2016 to help Trump through stolen electronic documents and misinformation.

The Washington Post contacted the 20 Democratic presidential campaigns this week to seek their policies on the use or referencing of material that was obtained through hacks or was otherwise stolen. Eighteen responded with statements renouncing such material to differing degrees, including one that reserved the right to use the information if it was verified in news reports. Two did not provide an answer.

Although Democrats agree that the posture of Trump and his associates is unnerving, there is less harmony among them about the steps they should take to dissuade foreign actors from sowing discord and avert unseemly tactics in the race. They are also dealing with hard feelings from 2016, when hacked emails showed how party leaders sought to thwart Sen. Bernie Sanders (I-Vt.), now a more prominent White House hopeful seeking the Democratic nomination.

The unfolding debate between the two major parties and within each one underscores the difficult questions that have charged into the 2020 contest: Will those seeking to stoke tumult unleash a new cache of private information? Would campaigns use it against each other? And how can they prevent it from happening in the first place?

“The idea of campaigns routinely using hacked material is disturbing. The idea of them doing it in conjunction with foreign governments is terrifying,” said Michael Steel, a Republican strategist who worked for Jeb Bush in 2016 and is calling on Trump to take a stand against stolen information. “At the same time, I worry that it may well be an epidemic in the 2020 election cycle.”

Although Trump recently distanced himself from WikiLeaks, as a candidate in 2016 he frequently praised the website, which published hacked Democratic emails that were unflattering to party leaders and diverted attention from issues he faced. The authorities said the emails were stolen by Russian operatives. Members of Trump’s campaign were in contact with the site, and Trump repeatedly urged his supporters to read the emails WikiLeaks published.

In July 2016, Trump publicly encouraged Russia to try to unearth private emails belonging to Hillary Clinton. “Russia, if you’re listening, I hope you’re able to find the 30,000 emails that are missing,” he said at the time.

Now, some wonder whether the position of Trump and his inner circle could pave the way to a new round of intrusion.

“There are a million ways you could see why this leads to negative externalities for campaigns,” said Republican strategist Rick Wilson, a vocal Trump critic.

Trump’s personal attorney, Rudolph W. Giuliani, said Sunday in an interview with CNN’s “State of the Union” that “there’s nothing wrong with taking information from Russians,” though he said he probably would not have accepted it as a candidate. Asked on NBC’s “Meet The Press” whether it was acceptable for campaigns to use material stolen by foreign adversaries, he replied, “It depends on the stolen material.”

Sen. Richard Blumenthal (D-Conn.) a member of the Senate Judiciary Committee, called Giuliani’s comments “pretty astonishing,” adding that he had to read them three times before he could believe what he was seeing. Blumenthal said that “both sides have to draw a line in the sand” against hacking and illegal interference.

The Post survey of the Democratic field yielded similar responses from campaign representatives, though the precise wording varied from one campaign to another.

“We won’t knowingly use hacked or stolen material,” said Ian Sams, a spokesman for Sen. Kamala D. Harris (Calif.).

“Julián Castro’s campaign will not knowingly use or reference materials obtained through illegal means,” said Jennifer Fiore, a spokeswoman for the former housing secretary.

“Our campaign condemns the use for political gain of information or material obtained by illegal means,” said Jeff Giertz, a spokesman for Sen. Cory Booker (N.J.).

Sen. Kirsten Gillibrand (N.Y.) issued a pledge to “not participate, aid, or encourage hackers or foreign actors in any attempt to influence American elections or the campaigns of their competitors” and urged her competitors to sign on.

Some Democrats have taken a keen interest in how the Sanders campaign plans to comport itself after a bruising 2016 campaign in which emails published by WikiLeaks angered supporters who felt the documents confirmed their long-held suspicions that the Democratic National Committee favored Clinton in the primary.

Sanders is also under scrutiny because the Mueller report found Russian actors were seeking to help his campaign in 2016. On April 15, his campaign manager accused the Center for American Progress (CAP) of opposing Sanders’s 2016 goal of a $15 minimum wage. The group did not take a position on that issue, but a hacked email released by WikiLeaks showed Neera Tanden, the group’s president, personally opposed raising the federal wage that high in private advice to Clinton’s campaign.

After initially indicating that the hacked email was the basis for its claim against CAP, a Sanders campaign aide later said that was not the case. The aide pointed to news reports about a 2015 CAP publication analyzing the economic impact of a $10.10-an-hour wage, which did not mention or oppose a $15 wage, and Tanden’s vote against a measure to aggressively push for $15 in the 2016 Democratic Party platform. The platform she voted to support ultimately did call for a $15 wage. Now, both Sanders and CAP agree on the figure.

“Bernie Sanders believes in a fully issue-based campaign, and we would not use stolen material to attack another candidate,” said Ari Rabin-Havt, chief of staff for the Sanders campaign.

The question of how campaigns might address hacked material that is later cited in news reports looms over the race. Patricia Ewing, a spokeswoman for Democratic candidate Marianne Williamson, said in an email that Williamson’s campaign would not knowingly use hacked material, but,“if something has been reported in the main stream press and verified, we reserve the right to reference it.”

The two Democratic campaigns that did not respond when asked their position on hacked materials were those of Rep. Tulsi Gabbard of Hawaii and tech entrepreneur Andrew Yang.

The interest in taking a clear position on hacks extends beyond the Democratic campaigns to the rest of the party. DNC Chairman Tom Perez wrote an open letter addressed to Republican National Committee Chairwoman Ronna McDaniel on Monday calling Giuliani’s comment an “affront to our democracy” and urging her to join his promise not to “seek out or weaponize stolen private data for political gain.”

In response, an RNC spokeswoman referred to a prior statement from McDaniel, stating, “Any breach of our political organizations — regardless of party — is an affront to all of us, and we should come together as Americans to prevent it from ever happening again. It’s important we do all we can to safeguard our future elections.”

Despite the efforts to go on offense against Republicans, not all Democrats have been satisfied with the positions party leaders and presidential candidates have adopted, wanting them to go even further to head off malfeasance.

“Refusal to forgo both hacking and the use of hacking materials is a great start, but clear stances on use of fake social media accounts, fake websites and images, high-volume bots, troll farms, and other illicit tactics in common use today by Russia, Saudi Arabia, China and other authoritarian nations will also be necessary,” said Simon Rosenberg, who was a senior adviser to the House Democratic campaign arm in 2016 and helped run a program to search for online election interference.

Four Democratic Party chairmen in early nominating states sent a letter to colleagues across the country earlier this year that proposed to initiate talks with the presidential campaigns, state Democratic officials and the DNC about “agreeing to a new set of norms for campaigns in this age of social media and disinformation.”

South Carolina Democratic Party Chairman Trav Robertson, who signed the letter, said it started as a civility pledge and grew into a larger endeavor. “We’re living in the day and age in which the most difficult thing to do is to get people to understand or recognize or the truth,” Robertson said.

The DNC did not have any comment on the proposal.