Americans waited almost two years for Special Counsel Robert Mueller to finish his investigation into the 2016 presidential election. They could be forgiven for celebrating after the report's release, and especially in its finding that no evidence existed showing Americans facilitated Russian efforts to interfere with and "sow discord" during the election. While Mueller's assessment about potential obstruction of justice was ambiguous, the sudden collapse of the Russia-collusion theory left voters with the impression that the country now could turn its attention to policy and the upcoming election.

But it's become apparent that Democrats have no intention of moving on. If the report closed out the first stage of the Mueller War, it appears to have also launched the second stage — one in which members of Congress will attempt to reshape Mueller's investigation to reach the conclusions they expected. The White House plans to fight this next siege more aggressively than it did the first time around — and it will likely prevail.

Democrats have made no secret of their intentions to conduct investigations into the Trump administration and President Trump himself. With Mueller conducting the special counsel probe, however, Democrats largely steered clear of pushing for separate investigations into Russia-collusion, preferring to focus more on regulatory differences, ethics concerns, and Trump's personal finances. Those efforts will continue no matter what.

Added to that now, however, are plans to essentially redo the Mueller investigation through the judiciary, intelligence, and oversight committees in the House. The focus will shift from Russia-collusion to obstruction of justice, which even Mueller himself found a murky legal ground. Some of the potentially obstructive conduct never happened at all, but manifested as "orders" Trump barked at subordinates, but that never got fulfilled. Other actions, such as the firing of former FBI Director James Comey — the catalyst for appointing Mueller to the special counsel position in the first place — involved "facially lawful acts within [Trump's] Article II authority." And, Mueller acknowledged, the lack of evidence of any underlying crime "affects the analysis of the president's intent."

Still, Mueller pointedly refused to state that Trump had not committed actionable obstruction of justice. "If we had confidence after a thorough investigation of the facts that the president clearly did not commit obstruction of justice," Mueller wrote, "we would so state." Instead, Mueller left that question open, and Attorney General William Barr and Deputy Attorney General Rod Rosenstein positively declared that no obstruction had taken place, after noting some disagreement with Mueller's legal theories on obstruction.

That was the equivalent of waving a red flag in front of an angry bull. House Judiciary Chair Jerrold Nadler (D-N.Y.) issued requests for all three to appear before his committee to explain the dispute. More provocatively, Nadler issued a subpoena to former White House Counsel Don McGahn, whose testimony comprises much of the 10 or more incidents Mueller reviewed for possible obstructive conduct. Nadler wants much more extensive recollections from McGahn on the record in the hope of building an obstruction case that will prompt a successful impeachment action.

This week, the Trump administration fought back in ways it contemplated but never used with Mueller. Presidents cannot claim attorney-client privilege for discussions with White House counsels, who technically serve the office but not presidents personally, but much of their work would be covered by executive privilege. Courts have recognized that privilege as necessary for presidents to get the fullest and most honest advice from staff, but not as valid when discussions turn to illegal activities.

Trump initially refrained from invoking executive privilege with McGahn, allowing him to speak to Mueller freely. But CNN reported late Tuesday that the White House is now preparing an executive privilege claim to keep McGahn from appearing at all before Nadler's committee or anyone else's. That tactic won't end with McGahn: Trump himself told The Washington Post that he could start staking out broad claims of executive privilege with any and all aides within his administration. If successful, those claims of privilege would prevent Nadler or any other Democratic committee chair from assembling any case for obstruction.

Trump argues that he cooperated fully with Mueller, even while protesting loudly about it, and enough is enough. "I could have taken the absolute opposite route," Trump pointed out. "I had my choice." At this point, Trump claims he will not allow a political party to conduct its own investigation where a special counsel has already done so. "There is no reason to go any further," Trump argued, "and especially in Congress where it's very partisan — obviously very partisan."

The Second Mueller War will be fought on two fronts. The courts in the D.C. circuit will get a lot of extra work sorting out the nuances of executive privilege, and it's not clear who has the better of that argument. Democrats will claim that privilege has already been waived once and for all time by cooperation with Mueller, but the White House will argue that the fresh venue and the politically charged nature of Congress allows for withdrawal of those voluntary waivers. Without formal impeachment proceedings — which House Speaker Nancy Pelosi (D-Calif.) is anxious to avoid — Congress' legal grounds for overturning legitimate privilege claims may well be insufficient.

The second front will be in campaign politics, and it might well be more fraught than the court battles to come. Voters generally don't like Trump much personally, but they've also just seen wild allegations of Trump being a Russian agent and/or stealing the election in 2016 collapse in Mueller's report on Russian collusion. Political partisans (and pundits, too, for that matter) might relish the conflict, but voters largely hoped that the Mueller report would put an end to this particular inside-the-Beltway feud and shift focus back to their priorities.

Instead, to paraphrase Al Pacino from another disappointing sequel: "Just when I thought I was out, they pull me back in." A decision by Democrats to pursue impeachment over an obstruction charge in a politically charged independent investigation would be risky — a lesson Republicans learned 21 years ago after the move to impeach Bill Clinton. The longer voters keep hearing about the non-collusion in 2016, the more Democrats risk major backlash in the 2020 election.