Safe to delete cache_form table while site is in maintenance mode? My site has a very large database of 100MB, most of this is in a table called cache_form.

I've tried clearing the cache. When I try and run the cron I just get a white screen. 

My site is in maintenance mode, is it safe to delete the contents of this table in PhpMyAdmin? There are clearly some other issues that I need to look into but is it safe to do this as a short term measure to get the site back on its feet? I've had to put it in maintenance mode as aspects of content creation have stopped working properly.
First off, cache_form is not really a cache table, but a temporary table used to contain data necessary to verify the form being submitted to Drupal is not forged.
If you were to empty that table, users would encounter validation errors for the data they submitted from the form they were using. Since the site is in maintenance mode, that should impact the only users who are allowed to access the site when it is in maintenance mode, which includes you. You just reload the page containing the form, and fill it again; it's not a permanent error.