In a crucial moment for Democrats, party leaders are hunting for a sweet spot that would satisfy their rival moderate and progressive wings on legislation to finance President Joe Biden’s multitrillion-dollar agenda of bolstering the economy and helping families.

With virtually no votes to spare and saber rattling by both Democratic factions, leaders are finding their search for middle ground arduous — even though the president’s push for infrastructure projects and family-centered initiatives is his top domestic priority.

With Sen. Joe Manchin, D-W.Va., winning the spotlight this year for pulling his party rightward by issuing demands on crucial issues, plenty of centrists and liberals are now using that same playbook. In a procession of meetings with White House officials and congressional budget writers, progressives have insisted that the emerging measures be big and aggressive, while moderates want them to be far more modest.

The leverage every Democrat has flows from simple arithmetic. Expecting unanimous Republican opposition to much of Biden’s package, they need total unity in the 50-50 Senate — plus Vice President Kamala Harris’ tie-breaking vote — and can lose only a very few House votes.