Pro-Immigration Rally at National Mall

Technically a closed open-air space due to government shutdown

It's officially underway, but it remains to be seen just how much of an impact it will have.

Advocates for an immigration reform bill are gathered Tuesday afternoon at the National Mall for a rally and march meant to draw attention to their cause. They had vowed to bring together "tens of thousands" of participants, but an actual head count as the event got started was not yet available.