You can easily attach polls to existing content. Polls may also be shared between content entries (and sites).
The poll setup provides a field 'selectedPoll' that you can add to your entry types (but you can use your own field too).
The field can also be used in matrix blocks if you use content builders.
Add the field to your entry's field layout:
You can then select polls from within your content entries:
{% set polls = entry.selectedPoll.all %}
{% for poll in polls %}
{% embed '_partials/poll_form.twig' with {poll: poll} only %}
{% endembed %}
{% endfor %}
You can also use the field to create a poll directly from a content entry such as an article: