As Democrats arm for more investigations, Trump insider confides, 'We're not ready' Democrats risk repeating key GOP mistakes from Clinton era, says David Bossie.

One of President Donald Trump's closest political advisers, a key combatant two decades ago in the impeachment battle against President Bill Clinton, says the White House and the Republicans in Congress are not sufficiently prepared for the investigative onslaught that he anticipates will dominate the remainder of Trump’s term.

“We’re not ready,” said David Bossie, a pugnacious Republican operative who served as Trump’s deputy campaign manager and has been counseling both the White House and congressional Republicans.

“Do I see a killer team that is ready for the impeachment proceedings that are potentially coming ... do I think the White House is ready? From a staff standpoint -- I would say no,” Bossie said. “Do I believe they are in the process of getting ready? Yes.”

Speaking on the ABC News podcast "The Investigation," Bossie said that a growing realization is taking hold of Republican Washington that the conclusion of special counsel Robert Mueller’s probe into Russian meddling in the 2016 campaign will only be the start of investigatory pressures on the White House. There will be need, he said, to address the inquiries as they migrate from the Department of Justice to Capitol Hill.

Both the administration and the Republican team in Congress now clearly recognize they need reinforcements, Bossie said.

Bossie sat down for an interview with “The Investigation” after having spoken privately with Republican minority leaders in the House of Representatives, which shifted into Democratic hands after the 2018 mid-term election.

“I told them that ‘you have to have a bigger staff and a bigger budget,’” Bossie said. “’If this investigation is going to get big and robust, you need more help and you need high-quality help.’”

Bossie has a wealth of experience in the bruising arenas of congressional investigations. In 1997, he served as the Republican’s chief investigator for the powerful House Oversight Committee, and his hardball tactics in scrutinizing Clinton’s role in the Whitewater land deal and questionable fundraising activity eventually prompted his resignation from the investigation.

Bossie has remained a lightning rod, forging a political operation that has produced a steady series of attacks on Democratic Party leaders since the early days of the Clinton administration. Much of that work sprung from Citizens United, a right-leaning group that has produced 25 documentaries since 2004 -- including six feature-length films in partnership with Trump adviser Steve Bannon -- and successfully sued to ease restrictions on campaign spending for corporations.

But with his party now in control of the White House, he has pivoted from offense to defense – to focus on helping Trump fend off investigative firepower coming from Democrats.

To date, Bossie told ABC News, he sees an operation in need of improvement. He said he was unsatisfied, for instance, with the performances by Republicans during recent congressional hearings with the then-acting Attorney General Matthew Whitaker, and the high-profile grilling of Trump’s one-time personal lawyer and fixer, Michael Cohen.

“I would have attacked Michael Cohen's credibility a lot more than they did,” Bossie said. “They did a decent job at it, but I think they could have gone much harder.”

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Ultimately, Bossie expects Trump to benefit from a “boomerang effect,” as the public grows weary of relentless investigative campaigns by Democrats.

He said he had learned from what he acknowledged was Republican overreach in efforts initiated in 1998 – efforts he himself helped orchestrate – to impeach Clinton. That effort ultimately failed in the Senate and Clinton’s popularity rose in the aftermath.

Bossie said Republicans “became so focused and so dedicated to the end result -- which we all thought would be impeachment -- that we really we overstepped, we overreached … We were hard chargers and we let that emotion of being caught up in it affect us as opposed to being dispassionate.”

“And I think that is what I look at today [with the House Democrats],” he explained. “I think that I see some of the same patterns and practices going on.”

Bossie said that he endorses the idea of the Mueller report being made public, “as much [of it] as humanly possible.”

He said it may prove appropriate to keep grand jury material secret, but even that could emerge later, as it did from the report that investigated Clinton. He said he has no insights into Mueller’s eventual conclusions but believes the probe will determine that the president did nothing to coordinate his campaign efforts with the Russian government.

“If it says there was no collusion, there was no cooperation no coordination,” Bossie said, “The American people will say, ‘OK, what are we doing now to benefit America?’ ... How are we getting back to business? What are we doing to move on from it?’”

"The Investigation" is a podcast series offering an in-depth look at special counsel Robert Mueller's investigation into Russian interference in the 2016 presidential election and its aftermath, analyzing the potential fallout and political consequences. Hosted by ABC News correspondent Kyra Phillips and the ABC News investigative team, led by Senior Executive Producer Chris Vlasto. "The Investigation" is available for free on Apple Podcasts (via iPhone), Google Podcasts (via Android), Spotify (via smartphone and desktop), Stitcher (via smartphone and desktop), TuneIn (via smartphone and desktop), the ABC News app (via your smartphone) or your favorite podcast player.