The infrastructure debate amounts to a political ultra-marathon for Biden and his Democratic-led Congress, a stark contrast with the mostly breezy path to approving Biden’s $1.9 trillion pandemic relief bill. Party leaders will be under immense pressure from their base to deliver, while also protecting the political future of their most endangered members, some of whom are already anxious about GOP attacks on proposed tax hikes, ahead of the midterm elections.

Pelosi has privately told her caucus that she aims to get the package through the House by the Fourth of July — an aggressive timeline that would give leadership roughly six weeks in session to finish assembling the package and secure the votes. Some senior Democrats are already warning that timeline could slip.

“The bigger it is, the more finesse you’ve got to have,” centrist Rep. Henry Cuellar (D-Texas) said in an interview. “Highways, infrastructure? Easy. Water projects? Easy. How you pay for it? Let’s take a look. And if you start adding climate? Well, what exactly are you talking about?”