Legal repercussions have arrived for the leaders of the effort to overturn the 2020 presidential contest, in what could serve as a warning to those who meddle in future elections.

Former President Donald J. Trump was indicted in Georgia on Monday, as were 18 others, including, from left, David Shafer, the chairman of the Georgia Republican Party; Sidney Powell, a lawyer; Rudolph W. Giuliani, Mr. Trump’s former personal lawyer; and John C. Eastman, a lawyer.