Watch live: Trump rallies supporters in Pennsylvania

Former President Trump will rally supporters Monday evening at Indiana University of Pennsylvania, a little over an hour outside Pittsburgh.

The Keystone State is a crucial prize in November's electoral count, and both campaigns have been working hard to win over voters in the state. The Harris campaign is deploying mobile billboards to Indiana, Pa., on Monday chiding Trump for his refusal to accept a second debate.

Monday's appearance also brings the former president within about an hour of Butler, Pa., the site of the July 13 attempt on his life.

The Secret Service recently made public the results of an internal review of their response to the shooting, and acknowledged communication and protocol failures that may have left Trump vulnerable.

Trump is slated to appear today at 7 p.m. EDT.

Watch the live video above.