Efforts to use the U.S. Constitution’s “insurrection” clause to bar former President Donald Trump from running for the White House again entered a new phase Monday in a hearing focused on whether the Jan. 6 Capitol attack meets the Constitution’s definition of the word and whether Trump’s role meets the threshold for being barred.

The Colorado hearing is the first of two states’ lawsuits that could end up reaching the U.S. Supreme Court. Monday’s testimony began with details about the 2021 assault that was intended to halt certification of Joe Biden’s election win.