How to denounce a white supremacist? Fundraise for refugees.

What do you do if one of your high school classmates grows up to be one of the most prominent leaders in America's white supremacist movement?

One answer, for those who graduated with Richard Spencer in 1997 from St. Mark's School of Texas, entails publicly condemning his racist agenda and raising money to help some of the people harmed by his rhetoric.

The response from the St. Mark's alumni is one example among many as liberal and conservative organizations alike have seen an outpouring of donations and volunteers – in volumes that some say is unprecedented – in the wake of the presidential election. While the election has placed pressure on the nation's widening political gap it has also galvanized and deepened civic engagement among Americans across the political spectrum.

Mr. Spencer's former classmates had raised more than $47,000 as of Monday afternoon for the International Rescue Committee (IRC), the primary organization that works to resettle refugees in the Dallas area, where the school is located.

"We proudly support IRC’s efforts and denounce those like Spencer who consider refugees a threat. Rather, like the many previous generations of Americans who have come here under similar circumstances, they are a source of American strength and pride," friends and alumni of the exclusive preparatory school's Class of 1997 wrote in the description of their online crowd-funding initiative.

Spencer is credited with coining the term "alt-right" in 2008 to describe his political views, which are a mix of conservatism, racism, white nationalism, and populism with an opposition to multiculturalism. Spencer has praised the victory of President-elect Donald Trump – whom the Ku Klux Klan and other racist groups have flocked to support – and Spencer drew widespread ire after he used Nazi-era propaganda to excite a crowd earlier this month at a conference hosted in Washington by the National Policy Institute, an organization focused on spreading identity politics in the United States, that he steers.

"Hail Trump! Hail our people!" Spencer called. "Hail victory!" came the response, as some saluted with a fully outstretched arm, according to a short video clip recorded at the conference published by The Atlantic.

Spencer's fiery rhetoric is far from the only cause that has spurred a flood of donations to nonprofit organizations in recent weeks. In the wake of this month's US presidential election, progressive groups especially have capitalized on unease following Mr. Trump's surprise victory over Democratic candidate Hillary Clinton.

Two days after the election, the National Immigration Law Center (NILC), published a call to action to challenge Trump's anti-immigrant positions.

"We strongly believe that his campaign promises would trample upon the civil and constitutional rights of many Americans and aspiring Americans, and we’ll use all the legal and political tools at our disposal to prevent the policies he actually enacts from harming our most vulnerable communities," NILC economic justice policy analyst Jackie Vimo wrote.

Five days after the election, the American Civil Liberties Union (ACLU) announced that thousands of people had volunteered their time and donated more than $7.2 million.

"This is the greatest outpouring of support for the ACLU in our nearly 100-year history, greater than the days after 9/11," ACLU executive director Anthony Romero wrote. "All of this support will be put to good use protecting the rights of all Americans."

Timothy Sandoval, who covers nonprofit fundraising for The Chronicle of Philanthropy, says the fact that these nonprofits have seen a post-election boost is unsurprising.

"Nonprofits often try to leverage big-news items like election results or other big political news or movements in order to raise money, and oftentimes they do see a bump in giving surrounding some of these big events," Mr. Sandoval tells The Christian Science Monitor. The extent of this year's boost, however, could be unprecedented, he notes.

"There are just many people out there who are upset and who want to do something other than post angry messages on Facebook," Sandoval adds, "so they’re giving to nonprofits who work on issues that they care about, or they’re signing up to volunteer because they see the stakes as extremely high this year."

In addition to the NILC and ACLU, post-election donors have given major funding increases to the Anti-Defamation League (ADL) and the National Association for the Advancement of Colored People (NAACP), as well as to groups that support lesbian, gay, bisexual, and transgender people, including the Human Rights Campaign and Lambda Legal.

Vice President-elect Mike Pence has long advocated for tighter abortion laws, both during his time in the US House of Representatives and as Indiana governor, so at least 20,000 people have made donations to Planned Parenthood since the election, making specific reference to Mr. Pence as their motivation (that's in addition to the more than 100,000 others who donated to Planned Parenthood without mentioning Pence).

Within 48 hours of the election, more than 500 volunteers applied online to work with the Council on American-Islamic Relations, the nation's largest advocacy group for Muslims.

"People are really concerned. They don’t know what’s going to happen to them, their families and their children in the next four to eight years. It’s really a frightening situation," Ibrahim Hooper, CAIR's national communications director, told Politico.

And environmental groups have shored up support as well, highlighting Trump's selection of Myron Ebell to head environmental issues on the transition team. (Mr. Ebell is "a climate contrarian" whose organization, the Competitive Enterprise Institute, is funded in part by the coal industry, as The New York Times reported.)

"Now it's time to turn that anger into action," Kierán Suckling, executive director of the Center for Biological Diversity, wrote in a letter soliciting donations from supporters. "The Center is going to be spending the next four years doing everything we can to stand between the Trump administration and the safety of our wildlife, the viability of our climate, the health of our people and the preservation of the wild places we all love. We'll do whatever it takes – in the courts, on the streets and in the halls of power – to win for the wild."

While support for progressive causes could be a way for disgruntled Trump opponents to channel their frustration into political action, conservative and apolitical causes have seen a bump, too, since the election, suggesting that there may be a more dynamic resurgence of political engagement at play.

Californians for Population Stabilization, which lobbies to reduce immigration, said online donations have increased dramatically, and anti-abortion group The Susan B. Anthony List reported a similar response.

In Minnesota, where the local Big Brothers Big Sisters mentoring organization typically sees a volunteer slowdown in November, organizers reported that more than 100 volunteers came forward the week after the election – triple the normal number of volunteers.

"We don’t know for sure why," Gail Vold Greco, the organization’s director of communications, told the Twin Cities Pioneer Press. "But some people have mentioned this is something specific and positive they could do in their community post-election."

This report includes material from the Associated Press.