In mid-November, as his House colleagues on Capitol Hill were consumed with questions about Ukraine and impeachment, Senator Mark Warner took to CNBC’s Squawk Box to discuss what he saw as one of the most important problems facing the country: Fitbit.

Or, more specifically, the danger of allowing Google to swallow up the personal fitness and health-monitoring gadget and its terabytes of consumer data. “The Fitbit deal needs a high, high level of scrutiny,” the Democratic senator from Virginia told anchor Andrew Ross Sorkin. “Large platform companies have not had a very good record of protecting the data or being transparent with consumers. I can’t totally blame them. If Congress doesn’t set rules of the road, asking them to self-regulate is, frankly, just not a viable option.”

Across the board, we as a country need to be hitting pause on the advances of Big Tech, Warner argued, channeling his inner trust-busting Teddy Roosevelt. He sees warning signs flashing all around, like Facebook’s fledgling attempt to launch a digital currency, Libra, and Google’s move into banking. Too much is happening without competition and government oversight, he said. “We have these giant tech platforms entering into new fields before there are some regulatory rules of the road,” Warner told CNBC’s viewers. “Once they get in, the ability to extract them out is going to be virtually impossible.”

The words coming out of Mark Warner’s mouth throughout 2019 would surely have stunned the Mark Warner who joined the Senate in 2009, amid the wave of techno-optimism that marked Barack Obama’s presidential victory and the early years of his administration. Back then it seemed everyone in Washington, Warner chief among them, thought tech was the solution, not the problem.

Yet more recently, in Donald Trump’s Washington, Warner has evolved into Capitol Hill’s most reluctant and thoughtful tech critic, grilling Facebook, Twitter, and Google executives, lashing out in private and public over their intransigence, and pressing the companies to confront the role their platforms have played in undermining democracy.

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As the vice-chair of the Senate Intelligence Committee, he’s also become one of Capitol Hill’s most vocal advocates urging the country to take foreign technology threats seriously, both the possibility of kinetic real-world cyberattacks (such as disabling power plants or water systems) and already-underway information influence operations like the ones that upended the 2016 presidential election, as well as the looming challenges next-generation technologies pose to national security.

Earlier this month, even as the president’s impeachment trial loomed for the Senate, he introduced—along with the chair of the Senate Intelligence Committee, North Carolina’s Richard Burr—new legislation aimed at closing the United States’ gap in 5G technologies with China by investing in Western alternatives to Huawei.

“Every month that the US does nothing, Huawei stands poised to become the cheapest, fastest, most ubiquitous global provider of 5G,” Warner said in announcing the new bill. “Widespread adoption of 5G technology has the potential to unleash sweeping effects for the future of internet-connected devices, individual data security, and national security.

Together, his views, advocacy, and legislative work over the past three years have put Warner at the intersection of the biggest stories in American politics—foreign interference in US elections, the evolving consensus that Big Tech is out of control, and the growing tech rift between the US and China.

It’s an unexpected role for a onetime venture capitalist who made a nine-figure fortune helping to usher in the technological age in which we all now live. And the 65-year-old senator remains enmeshed in the culture and politics of technology. His state is one of the top destinations for tech companies outside of the Bay Area (Amazon’s new HQ2 is being built in Arlington). He wears Allbirds—the official sneaker of startup bros—sports an Apple Watch, and dabbles in winemaking. Warner’s dotcom-billionaire friends compare their new Teslas and their private helicopters even as Warner’s political career has thrived thanks to his commitment to the same rural Americans who supported Trump.