A national campaign to impeach President Donald Trump has drawn some high-powered talent from legal academia.

Two organizations, Free Speech for People and RootsAction.org, have joined forces behind Impeach Donald Trump Now, a grassroots petition drive that has collected thus far more than 1.2 million signatures, and a lobbying effort on behalf of a congressional resolution calling for an impeachment investigation.

The campaign is aided by a 13-member legal advisory board, including: Harvard Law School’s Laurence Tribe and Lawrence Lessig; Steven Shiffrin of Cornell University Law School; Zephyr Teachout of Fordham University School of Law; Tamara Piety of the University of Tulsa College of Law; Catherine Ross of George Washington University Law School; Jennifer Taub and James “Gus” Speth of Vermont Law School; Nancy Leong of the University of Denver Sturm College of Law; and David Post (retired) of Temple University School of Law.

The board also includes two former state supreme court justices: James Nelson of the Montana Supreme Court and Fernande R.V. Duffly of the Massachusetts Supreme Judicial Court. Eva Paterson, president of Equal Justice Society, is also a board member.

The board advises Ron Fein, legal director of Free Speech for People, who has drafted the proposed congressional resolution on potential charges that could be brought in an impeachment, said Cornell’s Shiffrin. “We advise him as to, well, maybe you ought to word it this way, or not, or include it or not,” Shiffrin said.

There are “so many grounds,” said Shiffrin, adding, “I think the interference with the [Russian] investigation is a major violation of the rule of law and an impeachable offense. The conflicts of interest with respects to his businesses are to me a violation of the emoluments clauses. What you can’t impeach people for is simple incompetence, maladministration. That makes sense to me.”

The legal advisory board is “quite active,” said Ben Clements, board chair of Free Speech for People and partner in Boston’s Clements & Pineault. “We consult by email. When we are proposing changes or adding elements to the impeachment resolution, we generally run it by that group.”

When the campaign was launched shortly after the inauguration, Clements said, the focus was on Trump’s alleged violations of the foreign and domestic emoluments clauses. The proposed congressional impeachment resolution now has six categories of offenses, including obstruction of justice, abuse of the pardon power, advocating illegal violence and recklessly threatening nuclear war against foreign nations.

“We have been urging members of Congress to file a resolution that would begin an impeachment investigation,” he said. “We’re working with as many member of Congress and staffs as are willing.”

On the grassroots front, 16 cities and towns have passed impeachment resolutions, said Clements, a former federal prosecutor and former chief counsel to Massachusetts Gov. Deval Patrick.

Shiffrin is not optimistic about either a congressional impeachment investigation or impeachment itself. “I don’t see impeachment as very likely, because I think it would require Democrats to win the House. Given gerrymandering, I think it’s very unlikely the Democrats would win the House but if they did, then I think impeachment would occur,” he said.

Although also pessimistic, Clement said, “I still believe there must be a tipping point. I certainly think the legal, factual and constitutional basis for impeachment is compelling, bordering on overwhelming. It’s obviously a question of whether the political will is there. It’s clear it’s not there now, certainly not for Republicans.”