If an advertiser has the same keyword in 2 different ad groups, the one entered in a given auction will have the:
- highest Ad Rank
- lowest maximum CPC bid
- highest cost-per-acquisition (CPA) bid
- highest maximum cost-per-click (max. CPC) bid
Explanation:
When several broad match keywords in your ad group broadly match a search term, the system will prefer to use the keyword with the highest Ad Rank.
Read more here: https://support.google.com/Google Ads/answer/2756257?hl=en