WASHINGTON (Reuters) - Democratic presidential candidate Elizabeth Warren released information on Sunday about her past legal work, showing nearly $2 million in compensation from dozens of clients over the decades, as a dispute intensified with her rival Pete Buttigieg over transparency.

Warren, a leading candidate among the 15 Democrats vying for the party’s nomination to take on President Donald Trump in the November 2020 election, had already put out 11 years of tax returns in April and called on other candidates to follow suit.

Buttigieg, the mayor of South Bend, Indiana, has said in recent days that Warren, a U.S. senator from Massachusetts, should release older tax documents detailing her corporate legal work.

In return, Warren has called on Buttigieg to allow media coverage of his private donor events and to disclose information about his past work at the consultancy company McKinsey. Warren does not hold big-ticket fundraisers and has focused her campaign on combating Washington corruption and corporate greed.

Buttigieg’s campaign said on Saturday it was working on making the details of his employment at McKinsey “fully transparent” and called on Warren to match that by releasing her tax returns covering her corporate legal work.

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On Sunday, in a 15-page document, Warren’s campaign provided examples of her legal work, some of which dated back to 1985, in capacities including as a counsel, consultant and expert witness, giving information about the cases and how much she was compensated.

The document included dozens of cases, some of which Warren took on a pro-bono basis and was not compensated for. In some cases, she worked with a group of consultants. The document showed a total of nearly $2 million in compensation.

A Reuters/Ipsos opinion poll on Thursday showed that support for Warren dropped nationally to its lowest level in four months, as she came under attack over her proposal to extend government-paid healthcare to all Americans, deemed too costly by her rivals for the nomination.

Warren, 70, is still among the leaders in opinion polls in Iowa, which kicks off the Democratic nominating contests on Feb. 3, and in other early voting states. Buttigieg, 37, who had campaign stops this weekend in Iowa, has surged into the lead in recent opinion polls there.

The Reuters/Ipsos poll, conducted on Wednesday and Thursday, found the level of indecision had jumped among Democrats and Democratic-leaning independents after an already wide slate of candidates experienced considerable recent turnover ahead of next year’s election.