House Speaker Nancy Pelosi’s announcement that she is “not for impeachment” has caused resistance on the left. Pelosi is not trying to protect President Trump. She is trying to protect the Democratic Party from its lunatic fringe. It’s increasingly difficult.

Pelosi is the first House speaker in six decades to return to the job a second time. But the Democratic majority she now presides over is much different from the one she led in 2007. Since the 2018 midterm elections that gave her back the speaker’s gavel, her party has gone off the rails.

First, Rep. Alexandria Ocasio-Cortez, D-N.Y., hijacked Pelosi’s agenda by announcing her Green New Deal – a $90 trillion-plus miasma of government spending that proposes to provide everyone with health care, a government jobs guarantee, free education, medical leave, job training, retirement security and universal basic income to support those who, as she put in her infamous talking points, are “unwilling” to work.

Pelosi tried to dismiss the plan as the “green dream” and declared it “will be one of several or maybe many suggestions that we receive.” She favors a more realistic agenda of bolstering Obamacare, lowering the cost of prescription drugs, building infrastructure, passing gun restrictions and other conventional Democratic priorities. But many Democrats do not share her lack of enthusiasm for full socialism. Virtually every Democratic presidential candidate has some kind support for the Green New Deal, making a socialist takeover of the American economy the centerpiece of the Democratic agenda.

Pelosi has also had to deal with the mess created by another left-wing insurgent, Rep. Ilhan Omar, D-Minn., whose anti-Semitic remarks have exposed a virulent strain of anti-Jewish hatred that is gripping the left. A resolution condemning Omar’s anti-Semitism faced such intense internal opposition that Pelosi had to replace it with a version that condemned not just anti-Semitism but also all forms of hate – including “anti-Muslim discrimination and bigotry against minorities” – rendering it meaningless.

Pelosi’s next move was to try to head off a suicidal impeachment drive gaining strength on her left flank. Anticipating that special counsel Robert Mueller may not find incontrovertible evidence that Trump engaged in a criminal conspiracy with Russia to steal the 2016 election, Pelosi announced that “unless there’s something so compelling and overwhelming and bipartisan, I don’t think we should go down that path.” That won’t stop Rep. Rashida Tlaib, D-Mich., who vowed on taking office “to impeach the mother (expletive)” and has announced she plans to introduce a resolution to start impeachment proceedings.

Pelosi knows that such an impeachment effort would divide Democrats and might not even pass the House. And even if it did, there is zero chance that two-thirds of the Senate would vote to convict Trump for something other than a criminal conspiracy with Russia. A failed impeachment would energize Trump’s base, raise Trump’s approval ratings and alienate the very suburban voters Democrats just peeled away from the Republican Party to win the House majority in the 2018 midterms. Most important, she knows it would distract Democrats from the agenda Pelosi wants to pursue.

During a private meeting this week, Pelosi reportedly asked House Democrats, “Do we want to drag (Trump) down or do we want to lift people up?” The answer from the Resistance is becoming clear: Drag him down!

Pelosi wants to do more than resist; she wants to govern. She wants to enact legislation. To do that, Democrats need to win back the Senate and the White House in 2020. But the party’s Ocasio-Cortez-Omar-Tlaib wing seems determined to undermine that strategy by pursuing a platform of socialism, anti-Semitism and impeachment. If they prevail, not only would Trump not be impeached – he’d also likely win another term.

Washington Post columnist Marc A. Thiessen is former chief speechwriter for President George W. Bush.

Twitter: marcthiessen