Political Actions

I was wondering, can a tapped Vampire still cast his votes in a political action?

Yes. Best example being the acting vampire.
Only vampires in torpor and vampires whose titles are contested cannot cast votes.

EDIT:
Vampires in torpor cannot cast votes or ballots.
Vampires whose title is contested don't get the votes from their title to cast. They can cast votes / ballots if they gain some (Bewitching Oration).

Can a vampire with a contested title cast the vote he gained by another source than his title, like a Bewitching Oration ?

Pascal Bertrand wrote: vampires whose titles are contested cannot cast votes.

This is wrong.

Vampires with a contested title have no votes to cast.

Ohlmann wrote: Can a vampire with a contested title cast the vote he gained by another source than his title, like a Bewitching Oration ?

Yes, vampires with votes to cast can vote, except when explicitly prohibited by card text.

FAQ 3.23

FAQ wrote: 3.23 Which vampires can cast votes in which referendums? i.e. Who can vote when?

In general, all vampires may cast their votes in all referendums.
Specific card text is required to prohibit a specific vampire or a specific
sect of vampires from voting. The only cards which prohibit sects of vampires
from voting are as follows:
Closed Session
Private Audience
Cardinal Benediction
Investiture
and Bruce de Guy

In all other votes, every vampire that is not in torpor may cast their
votes in favor of or against the terms of the vote.

Correct correction from Adonai.
I skipped the "their built-in" part.

Does this also mean that a Vampire controlled by another Methuselah that is tapped can still use his title in a vote??