"I doubt it" and "I doubt that"

[Daruma]

Hello.

"Do you think you can come tonight?" "I doubt it."

Can I say "I doubt that" in place of I doubt it?

Thank you.

[PROESL]

Hello.

"Do you think you can come tonight?" "I doubt it."

Can I say "I doubt that" in place of I doubt it?

Thank you.

Once again, in a structural or grammatical way, it would be correct to use "that" in place of "it" in your example sentence. However, the first, and most natural choice, would be to use "it". Using "that" would likely occur in a statement to show disagreement of some sort.

Carol: I heard Joe is bringing his new girlfriend to the party next weekend. This is going to really upset Jill because Joe just broke up with her.

Ken: I doubt that. Jill's bringing someone to the party too. So the score's gonna be even in this "game". (gonna - informal and common pronunciation of "going to" among native speakers of English)