Investors are beginning to sour on some of the biggest tech companies since weekend revelations that data firm Cambridge Analytica improperly accessed 50 million users' data through Facebook's platform. Stock prices were down for Facebook and its competitors — Google, Twitter, Snapchat — in light of the quickly-evolving scandal.

Why it matters: Calls for tighter regulation around user privacy and data transparency could completely upend the powerful business models around tech that have for years served as lucrative investment opportunities. This is the first time investors have reacted this strongly to a controversy around user privacy or election manipulation. Shares remained high for most of these firms throughout the Russia probe.

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Data:; Chart: Axios Visuals

Unsurprisingly, Facebook's reputation has been hit hardest by the scandal. The company lost $64 billion in market value since the story broke this past weekend, Axios' Dan Primack notes.

The concerns are particularly heightened for open platforms that can more easily be abused by bad actors. Some of the biggest tech companies, like Google, Facebook and Twitter are built to be easily accessible to users and developers around the world. This has allowed them to develop massive user bases and a lucrative marketing business that we are learning now can be exploited.

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Updated 2 hours ago - Politics & Policy

Coronavirus dashboard

Illustration: Aïda Amer/Axios

  1. Politics: Chris Christie: Wear a mask "or you may regret it — as I did" — Senate Democrats block vote on McConnell's targeted relief bill.
  2. Business: New state unemployment filings fall.
  3. Economy: Why the stimulus delay isn't a crisis (yet).
  4. Health: FDA approves Gilead's remdesivir as a coronavirus treatment How the pandemic might endMany U.S. deaths were avoidable.
  5. Education: Boston and Chicago send students back home for online learning.
  6. World: Spain and France exceed 1 million cases.

Early voting eclipses 2016 total with 12 days until election

People stand in line to vote early in Fairfax, Virginia in September. Photo: Tasos Katopodis/Getty Images

Americans have cast more than 47.1 million ballots in the 2020 presidential election, surpassing the total early-vote count for 2016 with 12 days left until Election Day, according to a Washington Post analysis of voting data.

Why it matters: The election is already underway, as many states have expanded early and mail-in voting options because of the coronavirus pandemic.

What to expect from the final debate of the 2020 election

Trump and Biden at the first debate. Morry Gash-Pool/Getty Image

Watch for President Trump to address Joe Biden as “the big guy” or “the chairman” at tonight's debate as a way of dramatizing the Hunter Biden emails. Hunter's former business partner Tony Bobulinski is expected to be a Trump debate guest.

The big picture: Trump's advisers universally view the first debate as a catastrophe — evidenced by a sharp plunge in Trump’s public and (more convincingly for them) private polling immediately following the debate.