The $600 federal unemployment benefit expired 3 months ago. But millions of Americans will lose all of their jobless aid by year-end if Congress doesn't step in.

• It's been three months since the $600 federal unemployment benefit lapsed on July 31, depriving millions of a critical source of government help.
• Democrats are seeking to reinstate the benefit while the White House offered $400 weekly aid in its latest stimulus offer.
• Around 15 million people could exhaust their unemployment benefits by the end of the year.
• "If Democrats win the election, my top priority is gonna be to reinstate a benefit that will allow people to make rent, pay groceries and medicine, and provide economic relief to millions of working families," top Democrat Sen. Ron Wyden said in an interview.

Three months ago, the $600 federal unemployment benefit enacted through the CARES Act in March expired for millions of Americans. The measure helped buoy consumer spending and pumped hundreds of billions into the economy, and provided the unemployed with extra cash to buy groceries and pay rent.

The lapse deprived jobless people of a lifeline and left them to make ends meet with state benefit checks totaling 40% of their previous wages on average, or around $330 weekly. Nearly 23 million Americans are now receiving some form of unemployment benefits.

The White House and Democratic congressional leaders are discussing a $2 trillion package that could provide extra unemployment aid among other measures. The Trump administration put forward a $400 weekly benefit in its latest offer, but Democrats are pressing to reinstate the $600 weekly amount.

Now eight months into the pandemic, many jobless people are starting to exhaust their payouts as the pandemic rages on and outdoor activities become more limited with winter nearing.

Pandemic Emergency Unemployment Compensation — a federal program providing an extra 13 weeks of benefits after state unemployment insurance runs out — will end on December 31. Government data indicates 3.7 million people are currently receiving those payments, and the number is steadily rising as people who lost their jobs early on remain out of work.

Then, Pandemic Unemployment Assistance covers around 10.3 million gig workers, freelancers, and independent contractors that are typically excluded from the regular unemployment system. It will expire at the end of December without an extension from Congress.

A senior Democratic aide close to the negotiations told Business Insider on Friday that the Congressional Budget Office conducted an analysis indicating five million people on state unemployment benefits would exhaust all their payments by the end of the year. The statistic appeared in Pelosi's latest letter to Treasury Secretary Steven Mnuchin. The CBO did not respond to a request for comment.

Elizabeth Pancotti, an economist and policy expert at left-leaning group Employ America, told Business Insider the recent spike in virus cases could prompt renewed business closures and job losses. She argued it reinforces the case for federal unemployment benefits at a vulnerable moment for the economy.

"We're gonna see another round of temporary and permanent layoffs," Pancotti said. "The need for additional fiscal support for both workers and businesses is only strengthening."

There are two unemployed people for every job opening, according to the Bureau of Labor Statistics.

President Donald Trump approved a temporary $300 weekly benefit in August, but it lasted only six weeks and the disaster relief funding for it dried up.

Read more: MORGAN STANLEY: Here's how to trade the assets that have the most riding on Tuesday's elections — plus 5 investors can count on no matter who wins

Sen. Ron Wyden, ranking Democrat of the Senate Finance Committee and the legislative author of the lapsed benefit, told Business Insider reviving the measure is high on the Democratic to-do list next year.

"If Democrats win the election, my top priority is gonna be to reinstate a benefit that will allow people to make rent, pay groceries and medicine, and provide economic relief to millions of working families," Wyden said.

The prospect for additional federal action for millions of unemployed Americans largely depends on the election results. It's unclear whether a package will get passed in a lame-duck session after the election. House Speaker Nancy Pelosi said on Thursday she was still optimistic about the odds of relief legislation getting through Congress.

"I want a bill for two reasons. First and foremost the American people need help. They need real help," Pelosi said. And second of all, we have plenty of work to do in a Joe Biden administration.. so we want to have as clean a slate as possible going into January."

Read more: A Wall Street investment strategist breaks down what would be the worst election outcome for markets — and details what investors can learn about the implications of a Democratic sweep by looking at 2009