'When you're in a hole, stop digging': Clinton lawyer Greg Craig to President Trump

The man who was responsible for providing legal advice to former President Bill Clinton during his impeachment inquiry told ABC News' "The Investigation" podcast that President Donald Trump’s strategy to combat his own impeachment inquiry is “doing enormous damage to him.”

"When you're in a hole, stop digging," said Greg Craig, who served as assistant to the president and special counsel during the Clinton impeachment, directing his comments toward the president and his personal lawyer Rudy Giuliani.

House Democrats are currently charging forward with an impeachment probe into Trump after a whistleblower report revealed that Trump urged Ukrainian President Volodymyr Zelenskiy to launch an investigation into former Vice President Joe Biden's son, Hunter Biden, during a July phone conversation.

Since House Speaker Nancy Pelosi announced the formal beginning of an impeachment inquiry in September, the House has subpoenaed documents from multiple executive branch officials and offices, all of which have gone unanswered.

Craig said that the White House’s efforts to block House Democrats from accessing witnesses and documents they've requested as part of their probe could cause further legal trouble for Trump. According to Craig, the House of Representatives has "responsibilities to oversee the activities of bureaus in the executive branch" and the president's actions are barring it from exercising its constitutionally granted "supervisory authority."

"I think the process that the White House has adopted as of now almost guarantees that there's going to be at least one count of obstruction of justice," Craig said. "Because it's very hard to believe that their position is in good faith other than just trying to prevent access to evidence that's pertinent."

Craig said that the strategy Clinton adopted — which eventually led to his acquittal in the Senate — was to focus his energy on being “the very best president he could be” and leaving the legal maneuvering to his advisers.

Comparably, he said that Trump seems to have made the mistake of engaging "in the lawyering of his own case" and potentially “adding more fuel to the fire of those people who are trying to remove him from office."

Craig is no stranger to an opposition party leading the charge in an impeachment. When Clinton was impeached by the House, a Republican majority brought articles against him. Trump faces the same possible outcome from Democrats in the House.

Leading Clinton’s defense taught Craig several lessons, he said.

Impeachment, Craig said, consumes so much public and political attention that, so long as it lasts, little else can be accomplished.

"When you go down the impeachment road there is very little that's going on [in] the public domain that is as important," Craig said.

He added that he learned that "It is possible to have an impeachment in a divided country but it is impossible to remove a president from office unless there is a developed consensus or a bipartisan recognition that he should be removed from office."

Craig also emphasized that the decision to launch an impeachment is a "solemn and important occasion that requires gravitas." Pelosi’s attempts to move the impeachment along with speed and accuracy have appropriately demonstrated this gravitas, he added.

Craig also advised House Democrats to keep the scope of their impeachment investigation focused on the Ukraine phone call rather than broadening their investigation to include evidence discovered by former special counsel Robert Mueller as part of his investigation into 2016 Russian election interference and possible obstruction of justice by the president.

"I think it is clearly becoming the focus of this Ukraine conversation, the use of the presidential power in ways that are unacceptable and inappropriate and unconstitutional and inconsistent with his oath," Craig said. "That's what I think we are focused on and I think it would be a mistake to focus elsewhere."

Although Craig was a counselor for both Clinton and Obama, he recently found himself in the middle of his own legal battle, becoming the only Democrat to face charges as a result of former special counsel Robert Mueller's probe into Russian interference in 2016. Although he was ultimately acquitted, Craig faced charges of lying to federal agents about his lobbying work in Ukraine in 2012. Prosecutors alleged that Craig lied to federal agents and those lies helped him avoid filing under the Foreign Agents Registration Act, which requires individuals and entities acting as an agent of a foreign client to register under the Department of Justice.

Craig declined to comment on the case as part of his interview with "The Investigation" podcast.

With Ukraine back in the spotlight, Giuliani could be running up against legal challenges related to the same law. According to two sources familiar with the matter, federal prosecutors in New York are in the middle of an ongoing investigation into Giuliani's relationship with Lev Parnas and Igor Fruman, two business associates who were recently indicted on charges of conspiracy to commit campaign finance fraud, false statements to the Federal Election Commission and falsification of records.

Craig was reluctant to give advice to Giuliani, stating a lack of familiarity with facts related to his specific case. But he said that Giuliani and the president should both consider altering their legal strategies.

"I think the obstructionism and the reluctance to respect constitutional processes and institutional rights is doing enormous damage to him. It may help him with his base, that's a political consideration that I certainly am not equipped or prepared to comment about," Craig said. "But if he is, if he is pursuing a path that seeks to be vindicated with the Congress, I think the choices and decisions he's made so far are not helping him."