I think the cost is, he doesn’t attract anybody new/And that could be a cost

[Ostap]

“I think the cost is, he doesn’t attract anybody new,” says Lynn Vavreck, a UCLA political scientist and a co-author of Identity Crisis, a book about the role of race in the 2016 presidential election. “And that could be a cost. The man won by 77,000 votes in three states. If African American turnout goes back to the Obama levels, he needs more voters. He could be fighting the last battle.”
The Atlantic

Hello, teachers. Why does the second mention of "cost" go with the indefinite article?

 

[Skrej]

Because it's non-specific. It's just one possible thing that might cost the election. It's not necessarily the one single thing to cost the election. It might be that factor, combined with others.

 

[Ostap]

Because it's non-specific. It's just one possible thing that might cost the election. It's not necessarily the one single thing to cost the election. It might be that factor, combined with others.

But isn't it strange that after the author has already specified that cost, he still later refers to it in a non-specific way? It's like, "Hi, mom! This is the guy I told you about. He is a guy."

 

[Skrej]

Your example isn't quite the same. It would be if you said something like this:

"Hi, mom! This is the guy I told you about. He is a guy I met at school."

 

[Ostap]

Your example isn't quite the same. It would be if you said something like this:

"Hi, mom! This is the guy I told you about. He is a guy I met at school."

the guy I told you about
a guy I met at school

Both the lines above refer to the same guy but describe him in different ways. In the OP, if we remove the writer's words, we're left with this:

“I think the cost is, he doesn’t attract anybody new. And that could be a cost."

Both "the cost" and "a cost" seem to refer to he doesn’t attract anybody new.

O do I misunderstand?

 

[jutfrank]

You can understand this with the uniqueness rule:

I think the cost is, he doesn’t attract anybody new = There's only one cost being referred to.

And that could be a cost = This is one of multiple possible costs.

It's probably the change of reference that's confusing you here, which is understandable, but you should know it's not at all unusual for a speaker to make such a change.

 

[Ostap]

You can understand this with the uniqueness rule:

I think the cost is, he doesn’t attract anybody new = There's only one cost being referred to.

And that could be a cost = This is one of multiple possible costs.

It's probably the change of reference that's confusing you here, which is understandable, but you should know it's not at all unusual for a speaker to make such a change.

Yes, but what's still confusing me is why repeat the idea of "a/the cost"? I.e., we already know from the first sentence that it is "a cost" anyway, so what new information is added by the line "And that could be a cost"?

 

[jutfrank]

There isn't any new information. She's repeating her point.