@Walter Hinteler,
Today, at the "Stop the Brexit Landslide" rallye, two former PM's - John Major (Conservative) and Tony Blair (Labour) - joined up to urge people to vote tactically to stop Johnson getting majority.
Tony Blair said he’s "voting Labour" at the election but urges people to vote tactically to deprive Boris Johnson of a majority.
John Major (in a video message) said that tribal loyalty to a party has its place, but no single party had a monopoly on wisdom, and that: "Sometimes you need to vote with your head and your heart for your country and your future ... This is such a time."