“They’ve always been on a collision course because they’re in the same vortex of voters,” said Tom McMahon, the former executive director of the Democratic National Committee. “If you’re Elizabeth Warren or Pete Buttigieg, you have to do reasonably well in Iowa and New Hampshire to survive and advance, and what they’re realizing right now is the other may be blocking their path forward.”

The back-and-forth has broken into the open in the last week, as Warren and Buttigieg battled for the top spot in Iowa throughout the fall. Warren eclipsed former Vice President Joe Biden for the lead in Iowa by late September and led the field into October. But by November, Buttigieg, who sank millions into TV ads and grew his on-the-ground operation, jumped ahead in the first caucus state, leading the field in multiple polls last month.

“It appears that both campaigns believe that [Bernie] Sanders and Biden have a firm set of supporters, while Buttigieg and Warren are competing over everyone else,” said Sean Bagniewski, the chairman of the Polk County, Iowa, Democratic Party. “Both of them have overlapping voters, both feel like their organizations are in close competition for first and second place finishes” in Iowa.

But there is still more unknown from both candidates as they battle over transparency: the actual names on Buttigieg’s McKinsey client list, and Warren’s tax returns from before 2008, which Buttigieg’s campaign is still calling on her to release after her disclosure of the income she earned from corporate legal work.

Buttigieg’s campaign pledged to release a list of his McKinsey clients soon: “stay tuned,” Buttigieg’s senior adviser Lis Smith tweeted. Buttigieg critics have long questioned whether he worked for problematic or unethical corporations, as McKinsey has come under criticism for a series of controversial projects.

But “unless there’s a very unpleasant surprise on the list,” it likely won’t impact voters, said Tom Peters, a former management consultant at McKinsey and author of “In Search of Excellence.”

Starting Tuesday in New York City, Buttigieg’s campaign will “pool” its private, high-dollar fundraisers — allowing one reporter or a small group of them to attend events and email a report of what happened inside to the whole Buttigieg campaign press list. It’s a similar approach to the one Biden has taken.

The Buttigieg campaign also pledged to release the names of its “bundlers,” donors who have helped raise money for the campaign from other people, within a week. Buttigieg has not released a list of its top donors since April.

As Buttigieg’s campaign said it would open its fundraisers, it still jabbed at Warren in a statement, saying that “no other candidate for president has released the entirety of their tax returns since their education concluded,” Schmuhl said.

Warren has released a decade-plus of tax returns, though none pre-dating 2008, which would cover her corporate legal work when she taught at Harvard Law School. On Sunday, Warren’s campaign released an earnings breakdown, totaling $1.9 million, for the 42 cases she worked on during that period. She had released the client list earlier this year.

Warren’s campaign has argued that this accounting, coupled with the 11 years of tax returns she’s already released, provides a fuller picture of Warren’s financial history than her tax returns.

Though both Buttigieg and Warren’s campaigns sought to put the other on the defensive with their flurry of releases over the last 24 hours, it may not have broken through to those Iowa voters. Bagniewski, the Iowa Democratic official, cautioned that “it seems like both their advisers are paying too much attention to Twitter.”

“I don’t know that many people who care that much about it or who are following it,” Bagniewski said.

Still, Warren supporters credited the Massachusetts senator for pressuring Buttigieg into shedding more light on his fundraising and questioned what Buttigieg’s McKinsey client list will reveal.

“It's great that voters will have more transparency into the corporate CEOs Pete worked for and the big-money donors who decided to go all in for this 37-year-old mayor who lost his last two campaigns,” said Adam Green, the Progressive Change Campaign Committee co-founder, which has endorsed Warren. “Voters need Pete to address new concerns that at McKinsey he may have helped lay off workers in places like Michigan.”

Activists from the Sunrise Movement and the Democratic Socialists of America said they planned to protest Buttigieg’s fundraisers in New York City this week, calling on his campaign to release the addresses for the events.