Commentary One of the takeaways of President Joe Biden’s marathon press conference on Jan. 19 was his declaration that “I’m confident we can get pieces, big chunks of the Build Back Better law, signed into law.” One possible big chunk is some version of the bill’s $270 billion-plus new federal child care program. Sen. Joe Manchin (D-W.Va.), who, with Sen. Kyrsten Sinema (D-Ariz.), is blocking Biden’s massive spending agenda, reportedly supported federal funding for universal preschool in the course of ill-fated negotiations on the bill last year. The less-than-progressive Manchin and Sinema might be persuaded to get on board a possibly less expensive incarnation of the program in the 50-50 Senate whose tied votes are decided by Vice President Kamala Harris. But if they do, they will upend the lives of millions of working parents by destroying thousands of existing modestly sized day care businesses and facilitating a needless Washington …