public static function preload_popup( $popup ) {
		// Bail early if the popup is preloaded already.
		if ( in_array( $popup->ID, self::$loaded_ids, true ) ) {
			return;
		}

		// Add to the $loaded_ids list.
		self::$loaded_ids[] = $popup->ID;

		// Add to the $loaded query.
		self::$loaded->posts[] = $popup;
		self::$loaded->post_count ++;

		// Preprocess the content for shortcodes that need to enqueue their own assets.
		self::$cached_content[ $popup->ID ] = $popup->get_content();

		// Fire off preload action.
		do_action( 'pum_preload_popup', $popup->ID );
		// Deprecated filter.
		do_action( 'popmake_preload_popup', $popup->ID );
	}