Final answer:
A verbal phrase can be an infinitive, gerund, or participial phrase, each serving as nouns, adjectives, or adverbs in a sentence. For example, the phrase 'To talk about poll numbers at this stage of the election' is an infinitive phrase acting as the subject of the sentence, a noun function.
Step-by-step explanation:
To determine which phrase in a sentence is a verbal phrase, we must understand the different types of phrases and their functions in a sentence. A verbal phrase can be an infinitive phrase, a gerund phrase, or a participial phrase. An infinitive phrase begins with "to" followed by the base form of a verb and can act as a noun, adjective, or adverb.
A gerund phrase includes a verb ending in -ing that functions as a noun and can be the subject of a sentence, direct object, subject complement, or object of a preposition. Lastly, a participial phrase is formed when a present participle (verb ending in -ing) or past participle (usually a verb ending in -ed or -en) functions as an adjective.
Using the provided examples, in the sentence 'To talk about poll numbers at this stage of the election is simply counterproductive,' the infinitive phrase "to talk about poll numbers at this stage of the election" is the subject of the sentence, hence functioning as a noun.