WASHINGTON (AP) — Lawmakers' most consequential battle this year over President Joe Biden's expansive domestic agenda will snake through a legislative maze that's eye-rolling even by Congress' standards.

In a Capitol where procedures can be exasperating for outsiders to grasp on a good day, Democrats have concocted an elaborate choreography to fulfill Biden's multitrillion-dollar plans for supercharging federal infrastructure, address climate change and boost social programs.

Their aim is to make the most of their control of Congress and the White House for the first time since 2010. With paper-thin House and Senate majorities, here's a road map to how they hope to pull it off:

TWO TRACKS

Democrats are stuffing their priorities into two separate bills, which lawmakers hope to finance by raising new revenue.

One measure would include around $1 trillion for highway, water systems and other public works projects. Around $600 billion is new spending, the rest an extension of existing programs. Democrats and Republicans have negotiated for weeks in hopes of reaching compromise, and an early procedural vote on this measure could occur this week.

The other would spend $3.5 trillion over a decade for a sprawling grab bag of social and climate change programs. It faces likely unanimous opposition from Republicans, who complain it is wasteful and a Democratic excuse to raise taxes.

WHY TWO PATHWAYS?

Democrats hope enacting a public works compromise with Republicans would show they're following Biden's pledge of bipartisanship. The strategy might also help win moderates' support for the more expensive social and climate measure by curbing its price tag a bit.

Timing is key. To satisfy progressives worried that moderates leery of costs and tax increases won't back the second bill, House Speaker Nancy Pelosi, D-Calif., has promised to not hold votes until both measures are ready.

One asterisk — if bipartisan infrastructure talks collapse, that measure's $600 billion in new spending would likely end up in the larger package.

BIPARTISAN INFRASTRUCTURE BILL

An early outline of the $1 trillion measure includes billions for roads, public transit, railways, airports, water and power grid systems, broadband and electric vehicle infrastructure.

But lawmakers have long disagreed over how to pay for such projects. They've already dropped one proposal to raise funds from more robust IRS crackdowns on tax cheats, and remain stalled over where to find the money.

This measure would follow the usual legislative pathway to becoming law. Besides House passage by simple majority, any agreement would need 60 votes to defeat a GOP filibuster, or delaying tactics, and pass the Senate.

That means at least 10 Republicans would have to join all 50 Democrats. Even with popular infrastructure projects at stake, that may be difficult as both parties contemplate lines of attack for next year's elections for congressional control.

GO-IT-ALONE BILL

Initiatives that Democrats hope to finance in their $3.5 trillion package include new dental, hearing and vision benefits under Medicare, clean energy technologies, universal preschool for toddlers and tax breaks for families with children and for buying health insurance.

To cover its cost and flash populist credentials, Democrats would raise taxes on the richest Americans and big corporations and U.S. firms' overseas earnings, toughen IRS enforcement and let Medicare negotiate lower pharmaceutical prices.

Democrats say this bill will be fully paid for. But disputes among Democrats and strict calculations by the Congressional Budget Office, lawmakers' nonpartisan fiscal ledger-keepers, about the amount of revenue they're actually raising may force them to scale back their spending plans.

FIRST, A BUDGET

To shield the climate and social programs bill from a GOP filibuster, Democrats will need to first pass a budget resolution, which itself cannot be filibustered.

That resolution's approval is key because it triggers so-called reconciliation procedures, which enhance Congress' powers to reshape the federal budget. This process guarantees that Republicans won't be allowed to filibuster the crucial follow-up bill actually providing the money for Democrats' priorities and specifying which programs and taxes would be changed.

The budget blueprint will also assign congressional committees specific amounts of money to spend, or raise in taxes, as their pieces of Democrats' $3.5 trillion plan.

Detailed decisions on numbers and policies won't come until the subsequent bill is drafted, probably months from now. But Democrats have already begun negotiating among themselves so leaders can produce a budget with broad numbers that, they hope, will have enough votes to get the process rolling.

THEN, THE REAL THING

Once Congress passes a budget, it's crunch time on the next measure — a bill actually providing the money and carving up the $3.5 trillion pie.

Democrats will plunge into prolonged talks, with ideological and regional factions vying over fine print that will determine winners and losers. Demands, threats and general unpleasantness will be common as leaders labor to keep lawmakers from voting "no."

The package will need just simple majorities to pass the House and Senate.

By law, the Senate can spend up to 20 hours debating it. After that, senators can, and almost always do, offer unlimited numbers of amendments in a "vote-a-rama" that often runs overnight, producing politically difficult votes and exhaustion.

The Senate's nonpartisan parliamentarian can rule for the removal of any provision in the bill not directly related to the budget, or items whose budget impact is "merely incidental" to their intended policy changes. That could, for example, imperil Democrats' hopes of giving perhaps millions of immigrants a chance for citizenship.

NO GUARANTEES

To pass the behemoth spending bill, every Senate Democrat will need to back it and no more than three House Democrats will be able to defect, assuming uniform Republican opposition.

This means Pelosi and Senate Majority Leader Chuck Schumer, D-N.Y., have hard bargaining ahead with progressives demanding boldness and moderates insistent on limiting the measure's price tag and tax increases.

With so much at stake, failure would deal a grievously damaging wound to Democrats, including to the legacies of Biden and other leaders like Senate Budget Committee Chair Bernie Sanders, I-Vt.

The impetus to avoid that political blow could in itself help Democrats rally together and succeed, but the pathway is narrow and bumpy.