President-elect Joe Biden will enter office with no fast fixes at hand to stem a tide of online misinformation that has shaped election-year politics and, unchecked, could undermine his presidency.

Where it stands: Election and coronavirus misinformation spreading widely on digital platforms has already done serious damage to the U.S., and it's bound to go into overdrive as the Biden administration starts enacting its agenda.

The big picture: The internet isn't necessarily where conspiracy theories, rumors and targeted disinformation (intentionally spread misinformation) begin. But it's almost always where they put down roots and spread.

The misinformation flood has already accelerated political polarization and deepened the pandemic crisis.

• Most experts agree that President Trump's repetitions of unsubstantiated claims of election fraud qualify as misinformation. But every effort by online platforms to limit them triggers outcries of "censorship" from his supporters.
• After Biden's White House move-in date, we can expect less virus misinformation to flow directly from the presidential pulpit.
• But huge damage to public trust has already taken place as science has become politicized, and measures to toughen online platforms against new misinformation can't restore that trust.

Particularly concerning is the prospect of mis- and disinformation circulating to discourage people from getting a coronavirus vaccine once one arrives.

• “Obviously, disinformation around the election is important, but disinformation about the vaccine will have a body count," Alex Stamos, former Facebook security chief and head of the Stanford Internet Observatory, told Axios.
• One idea for stemming the damage: Stamos suggests designating vaccine distribution as critical infrastructure. That would authorize government cyber operators to monitor for disinformation and work with federal, state and local officials to stamp it out.

More broadly, Biden will have few remedies at hand to alter the broader dynamics that have unleashed the misinformation flood.

• Some Democrats have floated making platforms culpable for misinformation they fail to remove.
• But the two parties have very different conceptions of what should be done about online misinformation, and unless Democrats succeed in taking control of the Senate via Georgia's two runoffs in January, action from Congress is unlikely.
• Many Democrats view President Trump's executive order targeting Section 230 of the Communications Decency Act, which protects online platforms from lawsuits over moderation calls and user-posted content, as sloppy and unconstitutional. Its provisions will likely vanish after Jan. 20.
• The larger debate over whether to update Section 230 will continue. Biden himself wants to end the law.
• But revoking or limiting Section 230 protections could end up opening the misinformation floodgates, if platforms decide to moderate less so they're not liable as publishers.

A less dysfunctional approach to managing the pandemic by the Biden administration could help reset the misinformation environment, Karen Kornbluh, a former Clinton and Obama administration official who is now director of the German Marshall Fund's Digital Innovation and Democracy Initiative, told Axios.

• "There's a real opportunity to start getting people to feel more civic-minded and also help them understand how to get access to trusted information," she said.
• Such an effort could include something like a "digital version of FDR’s fireside chats walking people through the facts, the latest developments, and what they need to do to get through the emergency together."
• Another option Obama White House veteran and former Facebook policy staffer Dipayan Ghosh has suggested: The administration could strike an agreement with industry to share data on disinformation campaigns as they're spreading.

The bottom line: Combating misinformation is likely to prove Biden's toughest tech challenge. Other tech policy efforts on issues like the digital divide and antitrust action against Big Tech can float up and down administration priority lists, but taming misinformation's existential threat is in a class by itself.