WASHINGTON — For months, House Speaker Nancy Pelosi, D-Calif., cited one compelling reason to hold off impeachment proceedings against President Trump: “public sentiment.”

Pelosi regularly mentioned an Abraham Lincoln quote about shaping support for abolishing slavery – “Public sentiment is everything,” the future president said in a 1858 speech – to set up a precondition for launching an impeachment inquiry.

Now, Pelosi finds the Democrats with much stronger public sentiment than originally anticipated almost three weeks after she greenlighted an impeachment probe into Trump’s pressure on a foreign leader to investigate his domestic political rival.

Every public poll since that Sept. 24 announcement has shown movement toward an impeachment inquiry, but deeper inside the polls are even better signs for Democrats, and worse ones for Trump. For now, Democrats are standing on solid ground that, even though removing the president from office remains a long shot, they have a chance to move through this process without inflicting political pain on themselves and possibly creating an overall net benefit.

One critical way to understand how the ground shifted is by measuring each side’s most energized supporters, and for most of this year Trump’s fanatics far outranked the president’s most fervent opponents.

In four surveys, from January through July, The Washington Post-Schar School poll found those “strongly” supporting an impeachment inquiry ranging between 29 percent and 33 percent. Those who “strongly” opposed impeachment proceedings ranged from 42 percent to 46 percent.

Those findings echoed how the public reacted to the impeachment effort in 1998 of President Clinton, which never had much support and ricocheted against the House Republican majority in the midterm elections after they made it the centerpiece of their campaign that year.

Clinton and Trump’s standings could not have been more different two decades apart – the former’s approval rating never dropped below 62 percent in 1998, according to the Pew Research Center, while the latter’s has hovered around 40 percent this year.

Yet the public seemed just as reluctant to begin impeachment against Trump as voters were opposed to impeaching Clinton. That reinforced Pelosi’s calculation to hold back starting an inquiry out of fear it would backfire against Democrats in 2020 the way it did against Republicans in 1998.

But then came revelations, beginning with a whistleblower report, that Trump had pressured Ukraine officials to investigate a top 2020 Democratic rival, former Vice President Joe Biden, and his son Hunter.

Without the benefit of public polling, Pelosi shifted gears and began a formal inquiry, led by the House Intelligence Committee and other panels. A risky move that might still rebound against Democrats has paid off – so far.

In the weeks since the Ukraine story broke, the sentiment at the core has flipped. Now, 43 percent of voters “strongly” support Pelosi’s move to start impeachment proceedings, according to The Post-Schar Poll, while just 29 percent “strongly” oppose the Democratic inquiry.

Some veterans of the most recent impeachment war see a clear distinction in how the public viewed the two scandals.

“The public was actually ahead of the politicians,” Rahm Emanuel, a senior adviser to Clinton in 1998 who went on to serve in Congress, White House chief of staff and Chicago mayor, said in a recent interview. “The public knew there was distinction between a marital vow and a presidential oath.”

The Clinton impeachment trial set a standard. Will it resonate in today’s Senate?

In the Ukraine matter, Trump is directly involved in some of the actions, unlike the long, complicated special counsel investigation into Russia’s interference in the 2016 election that was designed to boost Trump over Hillary Clinton.

Dave Winston, a Republican pollster who served as a top aide to then-Speaker Newt Gingrich, R-Ga., in 1998, said that Bill Clinton’s admission of lying about an extramarital affair took the sting out of the impeachment movement back then, leaving the public to simply question whether the offense was impeachable or not.

Now, Winston believes Democrats and Republicans have political opportunities with the impeachment inquiry. “There’s just so much stuff swirling. I think the public is in a very fluid situation right now,” he said.

In The Post-Schar poll, for example, 53 percent of voters believe Democrats are “acting to uphold their constitutional duties” in starting the impeachment process, while 42 percent disagreed with that.

But 50 percent of voters believe Democrats are “distracting Congress from more important issues ” by starting impeachment. Voters have grown so deeply cynical of politicians that they are willing to believe the worst of both parties.

“They think the Democrats are motivated for partisan reasons, and they do think the Ukraine thing could be a problem,” Winston said.

Normally, a president in such peril would simply turn this fight into a battle between him and Congress – something Trump has been doing – and usually that sets a path to victory because Congress is such a reviled institution.

Public job approval for Congress, as measured by the monthly Gallup Poll, has not crested 30 percent since August 2009, and has only topped 25 percent just three times in the past decade.

Even at his lowest moment, 35 percent of Americans approved of Trump’s job performance, according to Gallup.

But there are some early signs that Democrats might be able to weather this storm, or at least that congressional Republicans could come out of this situation in much worse shape.

Asked if they approve of how Democrats have handled the impeachment inquiry, 49 percent said yes while 44 percent said no. Independent voters were split, 46 percent to 45 percent, over how Democrats had handled the inquiry so far.

But the public has a terrible view of Republicans so far, with just 33 percent approving of how they responded to the inquiry and 56 percent opposed to the party’s response.

A lot of this current standing could fall apart, particularly if voters begin to see Democrats turning the process into the type of political theater that confirms their most cynical instincts toward Congress.

Democrats, in some ways, are now taking Lincoln’s 1858 words to heart, not merely as observers of public sentiment but forcefully engaged in trying to shape voter’s minds to support their actions.

“Consequently he who molds public sentiment, goes deeper than he who enacts statutes or pronounces decisions,” Lincoln wrote. “He makes statutes and decisions possible or impossible.”

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