Tyler Mc's answer is not completely correct - while the Llywydd of the Senedd would indeed have the casting vote, they are not completely free to choose how to cast it. Standing Order 6.20 states:
Subject to Standing Order 6.21 (which relates to the Llywydd's right to vote in plenary proceedings requiring a supermajority), the Presiding Officer or Deputy may
vote in plenary proceedings only when exercising a casting vote. Where
there is an equality of votes a casting vote must be given:
- in the
affirmative where further discussion of the matter before the Senedd
is possible; and
- in the negative where further discussion is not
possible or where there is a vote on an amendment.
This is similar to Speaker Denison's rule, a convention employed by the Speaker of the House of Commons, described further in Erskine May here:
The occasions on which a Speaker is required to give a casting vote
are rare, and in seeking to deduce principles upon which a vote is
given, the precedents of the last three centuries are relevant.
Although the decisions of successive Speakers have not invariably been
consistent, three principles have emerged:
- that the Speaker should always vote for further discussion, where this
is possible, eg Mr Speaker Addington's decision of 1796;
- that, where
no further discussion is possible, decisions should not be taken
except by a majority, eg Mr Speaker Denison's decisions of 1861 and
- and that a casting vote on an amendment to a bill should leave
the bill in its existing form.
If the tied vote takes place during the nomination process for the First Minister, further roll-call votes must take place until one candidate receives an absolute majority of votes (Standing Order 8.2). Neither the Llywydd, nor the Dirprwy Lywydd may vote in the nomination.
This process occurred in 2016 - a 29-29 tie between then leader of the Welsh Labour Party, Carwyn Jones, and then leader of the Plaid Cymru, Leanne Wood, who was supported by Assembly Members from other parties. Eventually, a political solution was found, and Wood withdrew from the competition.
A similar process takes place in the case of tied votes which occur during the nomination of the Llywydd and Dirprwy Llywydd, and the nomination of committee chairs (Standing Order 17.2J), except that further secret ballots take place rather than roll-call votes.