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Nancy Pelosi is about to face the biggest challenge of her speakership

(CNN) Nancy Pelosi's place in the history books is already secure. She will always be the first woman ever to serve as speaker of the House -- and the first woman to do so twice. She helped usher the first major overhaul of the US health care system in decades through the House. She led the efforts to retake the House majority not once but twice,

But what happens over these next few weeks in the House's impeachment efforts will shape the final chapter(s) of Pelosi's legacy in an important way, providing perhaps the biggest challenge she has faced in her time as speaker.

There's little doubt that House Democrats -- led by Pelosi -- are in the midst of an inevitable march toward making President Donald Trump just the third president in American history to be impeached by the House. Pelosi's blessing on Thursday of the drawing up of articles of impeachment -- an effort that will be run out of the House Judiciary Committee -- was the final, formal step that ensures that outcome.

But because the House will almost certainly impeach Trump, however, does not make what Pelosi has chosen to undertake -- and what it could mean for her party and the country -- a simple thing. The impeachment of a president has both in-the-moment political ramifications, longer-term political impacts and, obviously, sets precedent for how future presidents can act and how Congress should respond.

And it's important to remember that Pelosi -- as recently as a few months ago -- didn't want any of this. Despite a majority of House Democrats being publicly in favor of opening an impeachment investigation, Pelosi resisted the pressure to offer that movement her support. Her hesitancy was based on a belief that impeachment is an extreme measure, only to be used when it can be done so with bipartisan backing -- and that if it is seen as a partisan endeavor, it could badly divide the country and create a volatile and dangerous political environment.

Pelosi changed that view when the news of Trump's July 25 call with Ukrainian President Volodymyr Zelensky -- and the pressure campaign by the White House to force an investigation into the Bidens -- surfaced.

It was clear that she felt as though her hand had been forced by Trump.

"So, for me, this is about honoring our oath of office, making sure that the Constitution is respected," Pelosi said when asked by CNN's Jake Tapper Thursday night why she had changed her mind about impeaching the President.

Her doubts -- or, more accurately, worries -- about what impeachment might mean for the country and her party haven't disappeared, however. Pelosi is the savviest Democratic politician active in party politics right now. She understands that even with the facts regarding Trump's behavior with Zelensky -- and his administration's broader campaign to pressure Ukraine -- that there remains the potential of major blowback for impeaching a president less than a year before he is up for reelection.

Those worries came into stark relief Thursday when, just hours after Pelosi announced her support for drawing up the articles of impeachment, New Jersey Democratic Rep. Jeff Van Drew announced that he was very likely to vote against any and all of those articles. Van Drew said that the impeachment process "is tearing the nation apart. ... And I want to bring people together."

Cracks like those in Democrats' unity attempts allow Trump and his allies to insist that even Democrats know that this impeachment effort is a bad deal. And if Van Drew goes forward with his plan to oppose the articles of impeachment, Republicans will cast opposition to the measure as "bipartisan." (Worth noting: So far, no House Republicans have said publicly they plan to support any effort to impeach Trump.)

What the Van Drew situation highlights is the incredibly delicate balancing act required on Pelosi's part. She must simultaneously do what she believes is the constitutionally right thing while also being ever mindful of the political repercussions of doing said thing.

Nothing -- especially not something as widely covered and with as much historical import as impeachment -- happens in a political vacuum. Pelosi, of course, knows this -- and, in her town hall with Tapper on Thursday, sought to address it. Here's the key bit of what she said:

"This isn't about politics at all. This is about patriotism. It's not about partisanship. It's about honoring our oath of Office.

"This is the first President, has committed all of these things, as the constitutional experts said yesterday, nobody efforts even come close, not Richard Nixon, even came close to his dishonoring his own oath of Office.

"So, no, this isn't - politics is not even a consideration in this. This is about 'Protect and defend the Constitution.'"

Which is the right thing to say publicly. But being aware of what this all will mean for the party she -- more than any other Democratic politician of her era -- has built, is also an essential part of assuring that the last chapter of Pelosi's life in politics ends on a strong note.

The intricacies and complexities of managing this impeachment effort are vast. And they don't end when the House, sometime later this month, votes to formally impeach the President. This is a moment that will require all of Pelosi's considerable political and people skills.

To her credit, she seems to understand the size of the task and the monumental efforts required of her. "I truly believe that the times have found us to save our democracy, defend our democracy for the people," she told Tapper.

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