It was like shuttle diplomacy, with the former second baseman bouncing between warring camps. In early 2016, with a bitter primary between Hillary Clinton and Bernie Sanders sapping Democrats’ energy and resources that could have been trained on Donald Trump, Faiz Shakir tried to broker a peace. A close aide for then Senate Minority Leader Harry Reid with deep ties in the progressive movement, Shakir was an intermediary among the various players as Reid tried to get Sanders to drop out gracefully. The effort failed. Vermont’s senator, buoyed by unexpected wins in primaries like Michigan, and embittered by biases at the Democratic National Committee, hung on through July. And Sanders never found the right role to help Clinton, Shakir admits now, wondering what might have been had Sanders agreed to lay down his sword sooner.

As hopes for a Clinton presidency turned to opposition to Trump, Shakir worked briefly for Sanders before seizing the chance to be political director of the American Civil Liberties Union — where he now guides a surprisingly prominent combatant in the resistance. But the divisions of 2016 remain unresolved for Democrats, as they figure out how to navigate a surge of left-wing energy for a party at its lowest point since 1921, with electoral wins hard to come by. Shakir “would be a strong voice for anyone to listen to carefully who’s thinking about leading this party,” says Matt Canter, a veteran Democratic strategist with Global Strategy Group.

That steady voice is the son of Pakistani immigrants, who brings scars from political fights and personal attacks to the crusade against Trump. Shakir, 37, grew up in Florida a baseball fiend — eventually converting his father from cricket. He played ball for four years at Harvard, but standing, as Shakir puts it, “5-foot-nothing and 100-nothing,” a professional career wasn’t in the cards. Instead, he slid into politics.

As a junior research staffer for presidential hopeful John Kerry’s campaign in the fall of 2004, Shakir was involved in the fight against the “swift boating” of Kerry’s Vietnam War record — a painful lesson in the power of conservative media and rapid response. Then he joined the Center for American Progress think tank, which has close ties to the Democratic Party, and helped launch the blog ThinkProgress, building it into a major brand of left-leaning reporting and analysis. (There were missteps, including Shakir misrepresenting himself as a conservative blogger to try to cover a Republican Senate campaign.) ThinkProgress, acting as the “tip of the spear” for CAP, in Shakir’s words, would at times ding Democrats for not being liberal enough, but Shakir was always careful to pick his spots. “What Faiz is best at is striking that balance between pressure and support that makes leaders listen to you,” says Adam Jentleson, who worked with Shakir at both CAP and Reid’s office.

If Rep. Keith Ellison, who ran for chairman of the DNC, is the most visible Muslim in American politics, Shakir could be the most powerful.

But he attracted plenty of critics on the right. A year after a 2011 ThinkProgress report called Fear, Inc. detailed a network of Islamophobic organizations, Shakir joined House Minority Leader Nancy Pelosi’s office, and FrontPage magazine (which had been named in the Islamophobia report) accused him of helping raise money for terrorists. The convoluted tale: In 2000 at Harvard, Shakir was co-chair of Islam Awareness Week. The week’s final event, which Shakir says he did not plan or attend, was in coalition with other local colleges and sent proceeds to the Holy Land Foundation, a charity supporting Palestinians. HLF was later shut down by the feds, and its leaders were found guilty of sending money to Hamas. Foes also labeled Shakir an anti-Semite, based mostly on personal tweets by people who worked under him at ThinkProgress. Shakir says the accusations have “no merit,” but they stung. “It cut pretty deeply,” Shakir says. “It’s the type of thing I’ve been working my life against. I was always deeply involved in forging relationships across ethnic and religious differences.”

Working for Reid, Shakir helped shape the centrist Nevadan’s moves toward the progressive base in his final term in office, Jentleson says, such as the senator’s flip to support an assault weapons ban. Shakir wasn’t dragging him there so much as showing the benefits of the positions — and warning when a stance risked pissing off the liberal base.

When the ACLU came calling after the election, Shakir saw an opportunity to rebrand an institution known for courtroom advocacy rather than the political kind. In March he launched the “People Power” program, which has now engaged more than 210,000 activists across all 50 states. The group doesn’t endorse in political races, but aims to pressure lawmakers on priorities such as blocking deportations.

While it retains the nonpartisan label, the ACLU’s political activity often casts the group in partisan terms. In May, it denounced a Trump executive order relaxing restrictions on political speech by religious organizations — ultimately choosing not to file a lawsuit. “Look, I don’t think anybody is surprised that the ACLU … love[s] to come out against Republicans,” then Deputy Press Secretary Sarah Huckabee Sanders told White House reporters. “They love to talk about debating tolerance except when it comes to people of faith.”

Shakir, along with the ACLU’s executive director, Anthony Romero, has become a face of the resistance. If Rep. Keith Ellison, who ran for DNC chairman, is the most visible Muslim in American politics, Shakir could be the most powerful, considering the funds at his disposal. Juiced in part by the ACLU’s fight against Trump’s travel ban, celebrities are helping raise money for the group, which brought in $80 million online in the first eight months following the election (a typical pre-Trump yearly online haul was $4 million). In April, Shakir gave a rah-rah speech at a benefit concert at the Staples Center in Los Angeles, organized by Zedd and featuring Halsey, Imagine Dragons, Incubus, Skrillex and others. “I didn’t anticipate having rock-star status,” Shakir says. It might be time for him to get used to it.