Is a subject pronoun needed in the second clause?

Question

The campaign is not only financially beneficial to that organisation but it also has a positive impact on the morale of the employees.

or

The campaign is not only financially beneficial to that organisation but also has a positive impact on the morale of the employees.

Is the subject pronoun (it)needed in the second clause?

Patients undergoing cognitive behavioural therapy will experience a positive state and it is expected to lessen their anxiety.

or

Patients undergoing cognitive behavioural therapy will experience a positive state and is expected to lessen their anxiety.

Is the subject pronoun (it)needed in the second clause?

Answer 1

The first sentence's structure is wrong. The "not only ... but ..." structure is trying to govern two predicates whose main verbs are different: "is" and "has", but the "is" has been put before it.

One way to fix this is to make the "not only ... but ..." structure govern two clauses. When it's used like that, the first clause's verb must go before its subject:

Not only is the campaign financially beneficial to that organisation, but it also has a positive impact on the morale of the employees.

But the clauses have the same subject, "the campaign"; couldn't that stay before the "not only"? This would be grammatical, but might seem unstylish seeing as the first verb is only "is":

The campaign not only is financially beneficial to that organisation but also has a positive impact on the morale of the employees.

Perhaps a slight rephrasing would be acceptable?

The campaign not only benefits that organisation financially but also has a positive impact on the morale of the employees.

(Incidentally, if the verbs were the same, then you could move the common verb to before the "not only ... but ..." structure. The resulting word-order would then be closer to the word-order in the OP.)

The campaign is not only financially beneficial, but also motivational.

Answer 2

The subject pronoun can be omitted in the first sentence as in both clauses the subject is the same (the campaign):

The campaign is not only financially beneficial to that organisation but (the campaign) also has a positive impact on the morale of the employees.

The subject pronoun cannot be omitted in the second clause as it's the subject (though a formal one) of the second clause:

Patients undergoing cognitive behavioural therapy will experience a positive state and it is expected to lessen their anxiety.

Answer 3

You can't leave out the pronoun in the second sentence, because otherwise it automatically takes the same subject as the subject of the first clause, and you get

[Patients] is expected to lessen their anxiety,

which not only is ungrammatical (it should be patients are) but also doesn't make any sense.

However, to avoid making it a garden path sentence, the second sentence should read this is expected to lessen ... . Otherwise, when people read it is expected, they will assume it is a dummy subject until they come to the end of the sentence, at which point they will have to re-analyze its grammar.