News Analysis Unions are among the biggest beneficiaries of President Joe Biden’s $3.5 trillion “Build Back Better” spending plan that has united Republican opposition while splitting Democrats in Congress during nearly round-the-clock negotiations seeking sufficient votes for passage. Senate Majority Leader Chuck Schumer (D-NY) must overcome opposition from two Democratic senators—Joe Manchin of West Virginia and Kyrsten Sinema of Arizona—who worry passage of the biggest spending bill in American history will severely damage the economy. In the House of Representatives, Speaker of the House Nancy Pelosi (D-CA) faces warring moderate and progressive factions, each of whom threaten to sink the reconciliation bill if fundamental changes aren’t made. Every change, though, risks reducing support from one faction or the other. Schumer must keep all of his 49 Democratic colleagues on board and hope for help from the Republican side. Pelosi has only a razor-thin majority and can afford to lose no …