If I combine credit cards from the same issuer will my credit score go down?
I have 2 credit cards from capital one and I want to combine the limits onto one card. Will that I hurt my score or make no difference since the available credit will still be the same amount?
Both cards have a 0 balance; I pay them off every month. I just want one less card to carry, but want the same limit on one card.

In the past if you canceled one of the cards, they would typically throw the limit from that card on your other card. That would not affect your credit at all, unless the card you canceled was the older card, eventually shortening the length of your credit history.
Of course in this age of uncertainty, they are cutting many credit limits, so it is hard to say if they would transfer some or all of the limit to the other card. But it wouldn’t hurt to request adding the limit to the other card in your cancellation letter.
Chances are, you will only be able to transfer the balance to the higher interest rate of the two cards and they won’t increase the limit. This would probably increase your debt percentage which could negatively impact your score. However, your score will rebound when you pay off the balance.
It might be smarter to just concentrate on paying off the higher interest rate card, while making minimum payments on the other. When you get the higher interest rate card paid off, just leave it open with a 0 balance.
You shouldn’t see a score drop when combining existing cards.
If you combine the cards and close the one, you will still have the history of the closed card reporting for about the next 10 years from date of closure.
Cap One will combine a higher interest card into the lower interest card. People do it that way quite often.
There may be a chance that Cap One won’t combine the full credit limit from the card you are wanting to close. At times they leave a very small portion remaining on that card, ie $100 or so. Since you’re carrying a zero balance on all? cards, you won’t be hit with a higher utilization because of that. Plus, what small amount you would be giving up now can be made up later with a credit limit increase.
They do prefer that both cards be at a zero balance when combining anyway.