A strong gust of wind could(1) topple(2) our little tent.
The helping verb is could
The main verb is topple
You can identify helping verbs in a verb phrase. Verb phrases consists of the main verb alone, or the main verb + helping verbs. The main verb always comes last in the verb phrase.
Other examples of verb phrases with helping verb (HV) and main verb (MV):
The prices of houses could (HV) fall. (MV)
They should (HV) wait (MV) before leaving.
