Welcoming the announcement
The public test is met as the line is going out on social media.
Call to action to voters
There is no call to action for voters. There is an implicit call to action aimed at other political parties, hoping to influence them to commit to the policy as well.
Theresa May has made the announcement in her capacity as leader of the Conservative Party. The message is positive about the announcement, and thereby implicitly positive about the Conservative Party.
Context and timing
The charity has campaigned on the issue for several years. The announcement is in the context of the election and her party’s manifesto, so there is a link to the election and voting. At this time the Conservatives are the only party to have committed to the policy, although later on other parties will announce commitment and the charity will put out similar positive lines.
How a reasonable person would see the activity
A reasonable person would think that the intention of the activity was to influence political parties to adopt the policy. They would not think that there was an intention to influence voters to vote for the Conservative Party, since the charity would put out similar lines if any party announced its commitment to the policy, as they in fact did later on.
The activity cannot reasonably be regarded as intended to influence voters to vote for a political party, so the purpose test is not met. Spending on the activity is not regulated.