They don't. I mentioned it before, political capital isn't scrapped together, or generated. You gain it in lump sums when you get elected, with kickbacks from bills, and occasionally through crisis. The infrastructure bill is their attempt to do the middle, but the problem is the red states -hate- it. What is more, kickbacks only work when the other side is at least neutral to you, not passively hostile like -every single red state-. And a crisis? HA! Right now the ghost of General Lee could personally blow up the white house, announce the hanging of every black in America, and qanon as his personal army... and it'd generate nothing.
Something those suggesting a crisis don't realize. You look to your -leaders- to lead you through a crisis. The problem? Not even -democrats- fully believe Joe Biden won legitimately. There is no bump for a crisis here because a minority of America actually views Joe Biden as the leader to lead them -through- a crisis.
I mentioned before the twin follies of the Democrats. A mixture of putting everything off until its a problem they cannot ignore and tunnel vision towards their believed solution.
Think of it in those terms, and realize this. The amount they will ignore and the degree the tunnel vision intensifies only get -worse- linearly to the size of the crisis.
Now, think of the size of the crisis, and think of the degree of tunnel vision and willingness to ignore future issues?
They believe that if they manage to gin up political capital through a successful resolution of the "Covid Crisis" they can go ahead and solve everything. They have completely tunnel-visioned to the idea of making the Delta variant the new Satan, 'defeating' it, and -sincerely believe- it will make them lauded as heroes.