Washington (CNN) President Donald Trump's pick to fill the job of White House counsel is an indication the White House is preparing for possible post-election legal brawls with Democrats over everything from the findings of special counsel Robert Mueller's investigation to possible impeachment if Democrats take over the House of Representatives.

Pat Cipollone is taking over an office formerly led by Don McGahn, whose last day at the White House was Wednesday. While McGahn was planning on leaving the White House, his departure was expedited by Trump's Tuesday announcement of Cipollone's appointment, sources say.

Should Democrats take over the House, the President's lawyers expect a flood of new oversight investigations of executive branch agencies, which the GOP-controlled Congress has largely avoided. Democrats are also expected to try to get access to materials from the Mueller investigation, which the President's lawyers argue should be protected by executive privilege. The President and his lawyers have also raised the likelihood of an impeachment battle, even though Democratic leaders have tried to avoid discussing the issue.

Cipollone's arrival marks an important change for the President because it means he will have a White House counsel who isn't sidelined by conflicts as a result of being a witness in the Mueller investigation.

McGahn and others in his office have provided interviews to Mueller as part of the investigation into whether the President tried to obstruct the inquiry. As a result, the President had to bring on Emmet Flood as his own special counsel to handle Mueller interactions on behalf of the President's office. The relationship between Trump and McGahn was further damaged when McGahn's clashes with the President became public knowledge in news reports.

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