Can you bid against yourself?

[Tonearm]

I'm about to roll out a lot of ads in the same campaign, and some could potentially be bidding on the same keywords. Will that increase my CPC?

[HelenDev]

Not sure about raising the CPC, as only one ad (usually the best performing one) will get shown, and presumably only one of your ads will even get entered into the bidding auction to be shown.

But it is generally not considered a good idea to have duplicate keywords, partly for your own sanity (it makes it harder to optimise your campaigns and see the wood for the trees) and I guess it is also an indicator to Google that your campaigns are not that well organised, which I think can reflect on the quality score and therefore the CPC of your whole campaigns.

[EvilSaint]

Duplicate keywords would mean that only one of the two instances will appear. This would probably be determined by the ads attached to the keyword and the history behind the keyword as well as the ad copy.

The disadvantage of multiple duplicate keywords is that you get your CTR split between two instances of the same keyword as Google would determine which keyword instance to trigger. This will affect your QS long term.

[Tonearm]

Thanks guys, I'll keep duplicates out of my keywords.