The package's architects argue that, in many ways, the bill will eventually pay for itself by boosting the inflow of tax revenue. That “dynamic scoring” strategy will help justify part of the steep price tag, though that method of paying for legislation has spurred criticism from both Democrats and Republicans in the past.

Investments like free community college, child care assistance and universal pre-kindergarten wouldn't pay off for well over a decade, however. So, for the bulk of the bill, top Democrats will need to offer up more concrete ideas for counterbalancing their spending — by way of tax hikes and a host of policy changes that are expected to deliver savings in short order.

Here is what’s on the table:

Kill the Medicare rebate rule — Democrats think they could scrounge up as much as $180 billion by rolling back a pharmaceutical policy Donald Trump finalized at the end of his presidency. If they succeed in altogether scrapping Trump’s rule, drugmakers could continue to give pharmacies money to ensure their medicines get choice placement on Medicare plans.

Those rebates can be as much as half the drug’s sticker price. And while they are not passed directly to consumers, insurers argue they use savings to keep premiums low.

Some Republicans in Congress are also warming to the idea of ditching the former president’s rebate policy and allowing the prescription perks to go on.

Hit ‘Mega IRAs’ — Democrats say they’re aghast that hundreds of Americans have IRAs worth more than $25 million, and nearly 30,000 have accounts with balances topping $5 million, while many others have little to no retirement savings. Going after super-sized retirement savings accounts like that could drum up substantial revenue for the $3.5 trillion plan, Democrats say, though an exact figure is unclear.

Roll back the corporate rate — It's a foregone conclusion that Democrats will propose undoing Republicans’ cut to the corporate tax rate — the question is by how much. It's a quick and easy way to raise a lot of money: Each percentage point increase generates roughly $100 billion.

Biden wants to raise it to 28 percent, from the current 21 percent, but that’s probably too high for most Democrats. A more likely outcome would be a boost to a rate in the mid-twenties, which even Sen. Joe Manchin (D-W.V.) has said he supports.

Punish scammers — Forcing companies to pay back consumers as restitution for scamming and deception is estimated to produce $29 million in savings over a decade.

A bill already passed the House this summer to empower the Federal Trade Commission to crack down, after the Supreme Court voted to nix the agency’s authority to return billions of dollars to people who have been defrauded over the last 40 years. When the FTC can’t return that relief to harmed consumers, the money would go to the Treasury, and the Congressional Budget Office predicts millions of dollars would flow to the federal government that way each year.

In the Senate, leaders in charge of policy to protect consumers are still working on a bipartisan plan of their own. Sen. Maria Cantwell (D-Wash.) — who chairs the Commerce, Science and Transportation Committee — said she hopes a final “FTC fix” can pass Congress before the $3.5 trillion plan gets rolling. But if not, granting that enforcement authority within the larger plan could help offset the cost of the behemoth package.

Tap foreign profits — Many Democrats want to raise hundreds of billions of dollars by also toughening taxes on big companies’ foreign profits. Some want to tighten the so-called GILTI rules governing “intangible” income from things like patents and other intellectual property. They also want to rewrite — or blow up altogether — another tax known as the Base Erosion and Anti-Abuse tax. Depending on what they do, Democrats could end up raising even more money here than they do with a corporate rate increase.

Siphon from drug savings — Senate Budget Chair Bernie Sanders (I-Vt.) has estimated they could draw as much as $600 billion from various policies to lower the cost of prescription drugs, empowering Medicare to negotiate prices with pharmaceutical companies and helping to offset the cost of the program’s expansion to cover dental, hearing and vision benefits.

But more moderate Democrats and those with districts home to prescription drug companies, like Sen. Bob Menendez of New Jersey, have raised concerns about the potential effects on drug research, development and innovation, complicating caucus consensus on the issue.

Hike the top tax rate — Many Democrats also want to undo Republicans’ cut in the marginal income tax rate. As part of their 2017 tax cuts, Republicans reduced it to 37 percent from 39.6 percent. Democrats want to go back to 39.6 percent. That would be a relatively easy lift for the majority party leaders, who previously increased the rate to 39.6 percent as part of a 2012 budget agreement.

Pare down Medicare Advantage — Lawmakers and outside groups have flagged some form of cuts to the Medicare Advantage system as a potential source of savings in the reconciliation bill. This could take the form of a reduction in the benchmark rate that the government pays private insurance plans to cover some Medicare enrollees.

Increase capital gains — Some Democrats want to hike capital gains taxes, though that will be more controversial, particularly when it comes to a proposal to end a longstanding provision in the code that allows people to pass assets on to heirs free of capital gains taxes when they die. Democrats are already getting an earful from farmers, small businesses and others.

Separately, Biden also wants to require people making more than $1 million to pay ordinary income taxes on their capital gains. The top rate is now about 24 percent.

Beef up IRS enforcement — Spend money to make money. That’s pretty much the approach Democrats want to take to crack down on tax cheats. The majority party wants to inject tens of billions of dollars into the IRS budget, in hopes of raking in more revenue by going after tax dodgers.

President Joe Biden has proposed an $80 billion increase for the tax collection agency, estimating that boost would result in $700 billion in new revenue.

The increase in IRS enforcement funding had been floated as a way to pay for the bipartisan infrastructure plan. But Republicans rebuffed the idea last month, leaving all of the projected savings to instead be used in the $3.5 trillion plan Democrats will try to pass on their own.

One major problem Democrats will face in claiming that savings: A two-decade-old rule prevents lawmakers from paying for legislation with money drummed up by efforts like boosting IRS audits.

Caitlin Emma, Rachel Roubein, Sarah Owermohle, Natalie Fertig, Alice Miranda Ollstein and Emily Birnbaum contributed to this report.