leave it at that OR leave it as that

1. Theodore Roosevelt, the twenty-sixth President of the United States, is this type, although he had his good side as well. Like most real life people, you can't just call him a egomaniac and leave it as that.

2. This is the best we can do. We'll have to leave it at that.

3. I can do no more. I will have to leave it at that.

which one is the correct form of the idiom?

thefreedictionary.com has leave is AT that

(http://idioms.thefreedictionary.com/leave+it+at+that )

Or, do you use both?

Only 'leave it at that' is idiomatic.

Leave it at that/Leave it as it is Emotion: smile