On a recent Saturday morning, Alex Soros put on jeans, a white T-shirt and a baseball cap that read “From the window to the Walz” and went door-to-door for Democrats in a Philadelphia neighborhood. No one seemed to recognize the scion of the Soros family. One woman trolled him: “Who do you think I should vote for? For Trump?”

Soros, the son of 94-year-old Democratic megadonor George Soros , has been everywhere this election season. And he is posting it all online.

Before he put on the Walz baseball hat—a reference to the 2002 hip-hop hit “Get Low” that has become a campaign meme—Soros hosted Tim Walz in his Manhattan penthouse. He rubbed elbows with Kamala Harris and the Clintons at a White House state dinner. At the Democratic convention, he watched with fiancée Huma Abedin from a super PAC’s luxury box, relaying his highlights on social media like a fan at a concert.

That is the access granted to one of the biggest donors of the 2024 election cycle. George and Alex Soros have spent more than $60 million on the 2024 election , including full-throated support of President Biden and, later, Harris. Foundations endowed by George Soros and led by Alex have meanwhile doled out more than $200 million this year promoting issues such as voting access and reproductive rights.

“Whether Trump gets elected or not—everything else doesn’t matter,” Soros said in an interview last week in his apartment. The presidential election could represent an inflection point for democracy, not just in the U.S. but abroad, he said.

Soros took over his father’s $25 billion philanthropic empire last year. He has been consumed by the 2024 elections ever since.

“For my father, it was, how do you succeed in getting closed societies to become open?” Soros said. “I think now the question is, how do you keep societies from becoming closed?”

For years, many doubted George Soros would ever cede control of his empire. Alex was an unlikely successor who gained his father’s trust over time. The two have different approaches to politics.

George Soros used a fortune amassed from trading to promote free societies. Despite his reputation as a Democratic kingmaker, the elder Soros often preferred writing opinion columns and position papers to glad-handing with politicians.

“He never saw himself as fundamentally connected just to the Democratic Party,” said Christopher Stone , former president of Soros’s Open Society Foundations. “It’s that the GOP he saw was not one he felt he could support.”

Alex, who turned 39 last week, is in deep with the Democrats. He is promoting candidates, meeting politicians and encouraging nervous party officials. His eagerness to engage with people is perhaps the biggest difference between him and his father.

“Alex is a deeply political animal,” said Ben Rhodes , a senior member of the Obama administration who helped start National Security Action, a center-left research organization backed by Soros’s Open Society Foundations. “He’s constantly meeting people, he just never stops going. He’s a roadrunner. He shows up everywhere.”

You can follow it all on his social-media accounts, which feature Soros traveling the world meeting with world leaders—and top U.S. politicians, like Walz. That has led some on the left to fret that a megadonor being so public about his access to important politicians could hurt their cause. His post with Walz , with a backdrop of his deluxe apartment and New York’s skyline, drew criticism.

“With respect, probably not helpful for you to put yourself in the story like this,” blogger Matthew Yglesias replied to Soros’s photo on X.

“I’d do it again, and I will do it again,” Soros said about the photo. The meeting was also covered by Harris campaign reporters, he noted, so its existence was already public.

Soros argues that being online helps refute the Republican notion of the Soros family as a shadowy cabal. His father mostly ignored what was said about him by the right.

“There’s a view that we are some sort of hidden conspiracy,” Soros said. “The way that you deal with that is to be open and transparent. I don’t think we should allow ourselves to be toxified.”

Friends say Alex’s comfort with social media and his more public life is a reflection of his youth and his desire to create a persona that is distinct from his father’s. Soros said his social-media posts are “making the point that you have to engage with certain people” to promote his stated goal of open society.

Soros attended more than 30 meetings and events at the White House in the past three years, according to visitor logs, including state dinners and a nine-person meeting with Harris in August 2023. Michael Fuchs , a former deputy chief of staff to Harris, has been working at Open Society Foundations since 2022.

Soros said he wouldn’t have a seat at the table if Harris were elected. “I’m not on the transition team,” Soros said. He suggested he is most interested in foreign policy and immigration issues. He said he last spoke with Harris in September when she called to wish him congratulations on his engagement to Abedin. (“She’s always been very nice to me—not that anyone’s mean to me,” Soros joked.)

Abedin herself is closely connected to the Democratic Party. She was a longtime aide to Hillary Clinton and worked for Clinton’s 2016 presidential campaign. She was formerly married to disgraced Democratic congressman Anthony Weiner , from whom she filed for divorce in 2017.

Soros has been an enthusiastic supporter of abortion-rights ballot initiatives that can both enshrine abortion rights in states and help turn out Democrats to vote. The family has put more than $5 million into such initiatives in Florida, Arizona, Nevada and Montana, among other states, a decision Soros said was “easy” to make.

During this election cycle, Soros felt strongly that Democrats should try to win the single electoral vote up for grabs in the Omaha, Neb., area , so he routed $200,000 to the state’s Democratic Party to register and mobilize voters at the start of the year.

After Harris became the Democratic nominee, Georgia suddenly looked more winnable to Democrats, including Soros, who then gave $10 million for a get-out-the-vote drive aimed at low-propensity voters. Soros and his father have put $10 million into a pro-Harris super PAC.

Soros is looking beyond the current election cycle by investing in a pipeline of younger Democratic politicians. He was an early supporter for Ruben Gallego , who is running for Senate in Arizona .

“He goes and meets with them and asks, ‘Does this person have the chops,’” says Svante Myrick , a longtime friend who leads the progressive People for the American Way, which receives funding from Open Society Foundations. “He likes to meet them and look in their eyes to see if they have charisma, if they’re honest, do they have what it takes to win.”

The wave of post-Trump-era rising Democrats like Raphael Warnock and Mark Kelly , Soros said, is “rich.” After meeting Texas Rep. Jasmine Crockett , who first contacted Soros via Instagram, he told a friend he felt she was “Nvidia stock,” a reference to the breakout chip maker.

Write to Maggie Severns at maggie.severns@wsj.com and Gregory Zuckerman at Gregory.Zuckerman@wsj.com