However I just cannot see how that can be done.
If I click on 'Create New Ad: Text Ad' link it allows you to make changes to the original ad (below all the keywords).
It also shows 'Ads (1 Deleted Ads, 0 Clicks)' implying that the original ad has been deleted.
I do not want to experiment as I am scared of losing my good CTR history. (if that still applies to Adwords - it's impossible for a non full-timer to keep track of best practices)
Once saved, this will run equally against the pre-existing ad -- as long as you uncheck the "Show better ad..." option under your Campaign Settings.
And then I presume each ad is rotated equally and the number of clicks is shown for each ad.
There are two options on how to show ads.
1. Rotate equally
2. Let Google show the ad with the highest CTR the most.
To choose which setting you wish enabled, navigate to the campaign settings. There's a check box called: "Show better-performing ads more often".
If it's checked, Google optimizes ad serving. If it's unchecked, then Google rotates them equally.