When a group of Democratic and Republicans senators assembled at the White House Thursday with President Joe Biden to announce an infrastructure deal, it was all smiles and celebration.

“Today is proof that bipartisanship is alive and well in the United States Senate, and in our country,” Sen. Krysten Sinema, D-Ariz., the lead Democratic negotiator, told reporters back at the Capitol.

The celebration for the eight-year, $1.2 trillion deal only lasted a few hours. Despite the marathon negotiations that led to the compromise, the hardest work lies ahead: cobbling together a coalition of progressives, Democratic moderates and – perhaps – Republican centrists to pass the traditional transportation funding bill while also pushing a more ambitious “human infrastructure” program that touches on issues like subsidized child care, home caregiving and climate change that only Democrats support.

Evidence of how complicated that will be was clear when Biden declared at the news conference he would not sign the bipartisan proposal into law without a more progressive budget package with “human infrastructure” elements also landing on his desk – only to carefully walk back those comments Saturday after some Republicans accused Biden of a bait and switch and hinted at backing out of the compromise.