WASHINGTON (AP) — As congressional investigations into Russia’s interference in the 2016 election are ramping up, so is the political division, raising questions about whether lawmakers’ work will be viewed as credible.

The House this week scheduled its first public hearing, which some swiftly dismissed as political theater. Even as lawmakers began to review classified information at CIA’s headquarters, Democrats continued to call for an independent panel and special prosecutor.

The dynamic underscored the escalating concerns about whether the Republican-led investigations will have the funding, focus and, perhaps most importantly, bipartisan buy-in to produce findings that are broadly accepted and definitive.

“To be honest, we don’t know yet,” said Rep. Adam Schiff, the ranking Democrat on the House intelligence committee, which is conducting a probe in the House. “I can’t say for certain whether that will be possible. I can only say it is very much in the national interest that we do so. Because we cannot allow this to become another Benghazi committee.”

Both Republicans and Democrats have their examples of misguided or failed investigations. For Democrats the cautionary tale is the years-long probe into the 2012 attack on the U.S. diplomatic compound in Benghazi, Libya. Congress spent millions on the effort and the Benghazi committee held four public hearings. But Democrats consistently dismissed it as a political witch hunt aimed at Hillary Clinton.

In the end, the committee issued an 800-page report and found no new evidence of wrongdoing by Clinton, but it did reveal that she used a private email server for government business, which dogged her presidential campaign.

Other efforts — Watergate, Iran-Contra and the probe into Wall Street’s role in the financial crisis as examples — are generally viewed as having risen above the partisan fray.

“The only investigations which have credibility are the ones which are truly bipartisan,” said former Sen. Carl Levin, a Democrat from Michigan, who ran many congressional investigations during his decades in the Senate.

“The leaders of the investigation — the chairman and the ranking member — must trust each other. That’s No. 1,” Levin said of how to run a bipartisan investigation.

On the House and Senate intelligence committees, that trust was shaken when the White House enlisted the Republican chairs to help push back on reports about Trump campaign officials’ contacts with Russia, one of the elements lawmakers are tasked with investigating. Both Sen. Richard Burr of North Carolina and Rep. Devin Nunes of California said they did not do anything improper.

Nunes, who was a member of Trump’s transition team, declared he had seen no evidence of improper contacts between Trump associates and the Russians as the investigation was just getting underway.

Successful congressional investigations also need to be funded. The Senate has approved $1.2 million for the intelligence committee for the Russia investigation, according to a person familiar with budget details who requested anonymity to discuss figures that are not typical disclosed. The House intelligence committee has requested additional money, as well, but that has yet to be approved.

By comparison, the Benghazi investigation ultimately cost that committee more than $7 million.

The second key to a successful investigation, Levin said, is that the committee staffers — a mix of Republicans and Democrats — work seamlessly together.

Levin said the staff needs to operate openly. They have to review documents together. They have to prepare witness lists together, interview people together, and do joint memos for the lawmakers together.

“They’ve got to work together,” Levin said.

And that work comes with some serious homework, said Dan Berkovitz, a former Senate investigator. There needs to be a thorough understanding of the facts surrounding the investigation, he said, which requires getting all of the appropriate documentation and interviewing all people with relevant knowledge. And good investigations take time, he said. Announcing the start of an investigation and scheduling a hearing on it weeks later “raises eyebrows.”

The House intelligence committee announced it would hold its first hearing on the matter on March 20. The FBI and National Security Agency directors have been invited as well as former top Obama administration officials.