The phrase "having a case" is often used to refer to someone who has a strong argument or evidence to support their claim. However, there are several synonyms for this phrase that can be used interchangeably, such as "making a case," "presenting evidence," "stating a claim," or "providing proof." These synonyms are useful in different contexts and can help add clarity and variety to your writing. For instance, you might use "making a case" when emphasizing the persuasive capabilities of someone's argument, or "presenting evidence" when discussing legal or scientific disputes. Ultimately, choosing the right synonym for "having a case" can help your writing convey the desired meaning and tone.