Mason City (CNN) - After more than a year of existential fighting within the Democratic Party over its direction, debates over which candidate is best suited to defeat President Donald Trump and a constant, ambient anxiety over the prospect of a nasty primary that could damage the eventual nominee, the Iowa caucuses are finally in sight -- and the leading contenders are still playing nice.
There have been a series of scattered scuffles, like the ongoing clash between Sen. Bernie Sanders of Vermont and Joe Biden over the former vice president's record on Social Security. But none have broken out into the brand of open political warfare that characterized the party's last two open primaries.
In interviews with veterans of the 2008 and 2016 campaigns, current and former Iowa Democratic Party officials, and aides to the current contestants, there is a common thread: Worries over sparking a backlash among primary voters have created a braking system that has largely subdued the kinds of personal, protracted and heated exchanges that characterized those past campaigns.
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The deep field, with at least four nationally viable candidates on the ballot in Iowa, has dampened any enthusiasm among the candidates to launch attacks that might be perceived as openly "negative." Campaigns that previously risked those kinds of splashes -- most notably those of former Housing and Urban Development Secretary Julián Castro and Sen. Kamala Harris of California, both of whom launched memorable debate night broadsides against Biden -- were eventually punished by Democrats in the polls. Both Harris and Castro have since ended their campaigns.
In the run-up to the caucuses, a broad consensus has emerged among the leading contenders: You might be able to land a blow against a rival, but it's just as likely to boomerang and damage your own bid. Meanwhile, the size of the field means that any potential pile-up will clear the road for someone else to zoom on through.
The specter of a second Trump administration, and concerns that any Democrat might be perceived as abetting it, even inadvertently, also looms forebodingly over the process.
"Voters are looking for people to be constructive. That doesn't mean that there is not a contrast. That doesn't mean that you are not going negative, but it does mean that you're not going negative in ways that might ultimately translate into a significant liability for the general election nominee," said Leah Greenberg, the co-executive director of Indivisible, a nationwide grassroots progressive group that has not yet made an endorsement.
For all their meaningful differences, there is a unifying fear among the Democratic candidates that is, at once, both selfish and selfless. None want to see their faces -- or their words -- weaponized by Trump in a campaign ad this summer or fall. Within the campaign's two ideological factions, there is a similar concern. Sanders and Sen. Elizabeth Warren of Massachusetts have, for all but a few days during the back-and-forth over whether Sanders told her, in 2018, that he didn't believe a woman could win the election, observed a "nonaggression pact" designed to keep the progressive wing at peace with itself. There seems to be a similar, if less obsessively analyzed, kind of de facto agreement among the campaign's leading moderates -- Biden, former South Bend, Indiana, Mayor Pete Buttigieg and Sen. Amy Klobuchar of Minnesota.
To the extent any bad blood has risen, it has mostly flown across those ideological lines. Sanders and his campaign have repeatedly questioned Biden's record on Social Security, and to a lesser extent, his vote to authorize the Iraq War. Biden hit back, accusing Sanders of pushing a dishonest narrative. But both candidates have taken steps -- especially when pressed by reporters on the trail -- to tamp down the appearance of a deeper personal rift.
The feeling among some in the Sanders camp is that, while direct attacks on rival campaigns can often be self-defeating, the strength of the senator's base gives him more leeway to throw elbows at opponents.
"One of the advantages that Bernie has is that he has an symmetrical advantage to go negative because his base is so loyal that I don't think people will peel off it," a Sanders aide told CNN, while also noting that it didn't make political sense, for now, to press it.
The candidates keep the gloves on
Still, Sanders moved quickly last week to put a pin in a more pointed and politically explosive charge from one of his surrogate supporters, Zephyr Teachout, a law professor and former Democratic candidate in New York.
After her publication of an op-ed that accused Biden of a "big corruption problem" -- a piece that was subsequently boosted by the senator's campaign -- Sanders took the unusual step of publicly apologizing to Biden, who promptly accepted. A brief exchange of digital ads over Social Security followed a day later, but the conflict has been mostly stop-and-start. It is a debate Sanders and his team clearly want on the table, but not enough, at this point, to frame in more damning terms.
Buttigieg, who has run one of the feistier campaigns, targeted Warren last fall over "Medicare for All," questioning her plan to pay for the national health insurance program that has become a catchall cudgel for the moderates. He also ran a TV ad in Iowa critical of Sanders' and Warren's tuition-free public college plans. But even then, Buttigieg didn't mention either progressive by name, instead saying in the spot that "some voices" were pumping a program that might turn off a large swath of the electorate.
More recently, Buttigieg's campaign has launched a number of fundraising emails to supporters arguing that Sanders would be a liability in November.
"Bernie Sanders is raising tons of money, he's surging in the polls, and he has dark money groups attacking his competitors," a recent email said. "If things stay steady until the Iowa Caucuses in just nine days, Bernie Sanders could be the nominee of our party."
"But," it continues, "we need a candidate who can beat Donald Trump in November -- and Pete is the candidate who is best positioned to do that."
Faced with questions from CNN and several reporters on Monday about the substance of the emails, Buttigieg refused to dig in or amplify them, and scrupulously avoided discussing Sanders by name.
"I think it's imperative that we beat Trump. I believe I'm the best candidate to do it," Buttigieg said when asked if he thought Sanders could not win. "I would be a nominee if we can hold this President to account for the way he's turned his back on workers, on farmers, on service members, and won't be afraid to go forward and do that."
When the candidates do go after each other, it is often executed with such subtlety that many observers could be forgiven for missing the connection.
Klobuchar delivered that kind of vague attack on Tuesday, when, in an interview with CNN, she observed that impeachment is "not a game" because she is "actually in the arena."
"I can't, like, turn off the TV or change the channel to watch cartoons," Klobuchar said in Council Bluffs. "I'm on it."
The line mirrored something Buttigieg had said earlier in the day, when he told an audience in Indianola, "I live and breathe politics, and I'm exhausted watching the coverage of what is happening in our nation's capital." He added that he thinks it's all "by design to make us want to switch it off -- just watch cartoons or something and get a break."
2008 and 2016 loom over 2020
If the 2020 contest has fallen somewhere short of the platonic ideal of an entirely "positive" campaign, veterans of the primaries that pitted Hillary Clinton against Barack Obama in 2008, and Clinton against Sanders four years ago, are quick to note how much closer it's come.
Democratic voters and party leaders "are looking at 2016 through a microscope and not wanting to make the same mistakes, therefore we have a much more timid primary season," said Patti Solis Doyle, Clinton's 2008 campaign manager and a CNN commentator. "That wasn't the case in 2008. We had some experienced campaigners. We had a Clinton in the race, which, back in '08, the Clinton machine was identified with war room-style tactics, and we used them. And our opponents weren't shy about right back at you."
Solis Doyle and others also pointed to Trump as the individual who, when all else fails, functions as the ultimate peacekeeper.
"There is a fatigue that surrounds us all, Democrats and Republicans. And if you are going to run against Trump, part of your message is, 'I am not going to do that. I am normal. If I am president, you don't have to check your phone in the morning to see what I did overnight,' " she said. "There is this level of calm and comfort that voters are looking for, and they don't want the frenzy and aggressiveness that we all sort of live with day in and day out."
The hesitance among the candidates to be perceived as an attack dog, or as endangering the broader effort to defeat Trump, has been most sharply reflected on the airwaves.
According to Kantar/CMAG, which tracks and characterizes the candidates' TV commercial messaging, the overwhelming majority of ads run in Iowa -- more than 122,000 -- from January 5, 2019, through January 24, 2020, have been "positive" in tone. Over that period, the group counted only 11 ads it described as "negative." A little more than 1,000 others fell under the "contrast" heading, which includes more tepid spots that might only graze a competitor.
Matt Paul, who ran Clinton's 2016 campaign in Iowa, chalked up the campaigns' caution to the size of the field and the sensitive nature of the state's Democratic electorate.
"There is always a danger in Iowa if you go too negative, too fast, and certainly if it is perceived as personal, it can quickly backfire," Paul said. "But it is puzzling to me that they have waited so long to find the contrast. Even in the debates, there have been dust-ups, but not to the level of intensity that you would expect."
Going back to 2008, he noted, the "smaller field" meant that even relatively minor bouts were "magnified" because Obama and Clinton were, even before the caucuses, the clear standouts.
"I think with a larger field, people are waiting for the race to shape up," he said.
One reason operatives believe that 2008 and, to some extent, 2016 were meaner than this contest is that the candidates were running for an open White House.
Bad memories of the 2016 primary and its fallout have also shaped the discourse over the past year.
Sanders, despite being the most aggressive campaigner, often couches his criticism of Biden with the caveat that the former vice president "is a friend of mine," and has repeatedly sought to put voters at ease -- and calm their post-2016 anxieties -- by reminding them of his promise to back the eventual nominee, no matter how the contest plays out.
When Trump tried to stir the pot on January 17 by accusing the Democratic Party of "rigging the election again against Bernie Sanders, just like last time," the Sanders campaign knocked down the claim in a statement that evening.
"Let's be clear about who is rigging what: it is Donald Trump's action to use the power of the federal government for his own political benefit that is the cause of the impeachment trial," Sanders said in a statement. "His transparent attempts to divide Democrats will not work, and we are going to unite to sweep him out of the White House in November."
It was a telling note of caution from a campaign, and candidate, that has rarely been shy about criticizing the Democratic establishment. And for good reason. Scott Brennan, the Iowa Democratic Party chair during the 2008 caucuses, was instantly unsettled by the mention of 2016 -- and warned that voters in the state felt the same way.
"Maybe I have tried to forget about it (the heated nature of that primary) and you have dredged up some old wounds," Brennan told CNN. "I think a lot of what is driving this is 2016 here was so testy and the animosity remained well after the caucus. So now Iowans have kind of spoken and said, 'We hated that, so don't do it again.' "