Glad you asked. There are two pictures in each tweet, shown left and right. You can click on each to see the full picture. Each picture is actually two portra

Glad you asked. There are two pictures in each tweet, shown left and right. You can click on each to see the full picture. Each picture is actually two portraits (Mitch McConnell and Barack Obama), one above one below, separated by a big gap. Since apparently Twitter automatically chooses to crop pictures in default tweet display, the OP posted different cases to see where Twitter would crop the image. And it happens that Twitter chose one of the portrait always, until the OP reversed color. Some people wonder if it is because Barack Obama is black. Whether that's the reason or not, the observable fact remains.