After months of painstaking haggling, the U.S. Senate voted Tuesday to approve a historic $1.2 trillion bill designed to upgrade the nations aging infrastructure system by repairing and constructing new roads, bridges, airports, waterways and more.

If approved by the House, the legislation would provide the largest federal investment in infrastructure in decades. It would also mark a major victory for President Joe Biden , an avid railway fan who pledged to restore bipartisanship upon taking office.

The vote was bipartisan, with 19 Republican senators joining every Democrat in favor.

The Infrastructure Investment and Jobs Act includes more than $175 billion for building and repairing roads, bridges and railroads; $39 billion for public transportation and $65 billion for expanding access to high-speed internet. It includes tens of billions more to improve electric and power grids and make school buses and ferries more environmentally friendly.

The legislation also includes $15 billion aimed at replacing the nations lead pipes and service lines, a big part of Bidens pledge to aid overlooked and marginalized communities.

The financing of the package, which includes $550 billion in new spending, presented the biggest obstacle for the bipartisan group of senators 10 Republicans and 10 Democrats who spent months working to draft it. They ultimately settled on a mix of various revenue sources including obscure budget maneuvers, fees, and asset sales without raising taxes to cover the cost of the new spending.

The Congressional Budget Office, a nonpartisan scorekeeper, said that roughly half of the bill would be paid for, with $256 billion added to the deficit over the next 10 years. That analysis fueled GOP opposition to the measure, especially among self-described deficit hawks.

But the bills authors countered that CBOs analysis neglected other savings included in the bill, such as roughly $200 billion previously allocated to address the COVID-19 pandemic and unspent unemployment insurance funds. The provisions, Sen. Mitt Romney (R-Utah) argued, dont score under [CBOs] rules, but they are real dollars.

The path ahead for the bill is unclear, however.

House Speaker Nancy Pelosi (D-Calif.) has vowed not to allow a vote on the bipartisan legislation without the Senate first approving a $3.5 trillion reconciliation bill a partisan proposal to address the many policies (like child care, paid leave and climate provisions) that Republicans refuse to engage on.

Democrats on Monday unveiled their outline for the bill, a list of instructions for relevant Senate committees tasked with writing its various components. It includes huge liberal priorities such as paid leave, monthly checks for parents, immigration reform and new Medicare benefits.

A budget should be a statement of our values, and this budget is a clear declaration of the value that congressional Democrats place on Americas workers and families, Pelosi said in a statement, praising the transformational document.

The reconciliation process allows Democrats to avoid a GOP filibuster, but it requires every member of the Democratic caucus to vote for the package, even those who have concerns with the $3.5 trillion price tag like Sen. Kyrsten Sinema of Arizona and Joe Manchin of West Virginia.

House progressives, meanwhile, are flexing their muscles by threatening to vote against the bipartisan infrastructure bill if their Senate counterparts decrease the size of the reconciliation package. A protracted standoff between the partys two ideological wings could derail both bills and blow up Bidens legislative agenda, which got a huge boost this week.

The more immediate challenge for Democrats this week, however, is staying united in response to numerous amendments Republicans are expected to offer to the Democratic budget resolution amendments that are often messaging bills designed to exploit divisions within the party on taxes, spending, immigration and other issues ahead of next years midterm elections. The so-called vote-a-rama, a grueling marathon of votes, could last many hours and potentially even days.