Fox News, one of the most powerful and profitable media companies, will defend itself against extensive evidence suggesting it told its audience a story of conspiracy and fraud in the 2020 election it knew wasn't true.

The jury will be asked to weigh lofty questions about the limits of the First Amendment and to consider imposing a huge financial penalty against Fox. Some of the most influential names in conservative media — Rupert Murdoch, Sean Hannity, Tucker Carlson — are expected to be called to testify. But there is another fundamental question the case raises: Will there be a price to pay for profiting from the spread of misinformation?

Few people have been held legally accountable for their roles in trying to delegitimize President Biden's victory. Sidney Powell, a lawyer who was one of the biggest purveyors of conspiracy theories about Dominion Voting Systems, the company suing Fox for $1.6 billion, avoided disbarment in Texas after a judge dismissed a complaint against her in February.

Jenna Ellis, an attorney who worked with Ms. Powell and the Trump campaign, received a reprimand last month instead of losing her license with the Colorado bar. Donald J. Trump, whose false insistence that he was cheated of victory incited a violent mob on Jan. 6, 2021, is running for president a third time and remains the clear front-runner for the Republican nomination.

Political misinformation has become so pervasive in part because, there is little the government can do to stop it.

"Lying to American voters is not actually actionable," said Andrew Weissmann, the former general counsel of the F.B.I. who was a senior member of the special counsel team under Robert S. Mueller that looked into Mr. Trump's 2016 campaign.