Blair has been a remainer for some time, at least since his speech in 2012 on Europe.If it did it was a brief journey.
That was in 2012.The short term politics are clear: being anti-Europe is today popular. However leadership is not about conceding to the short-terms politics. It is about managing the short-term politics in the pursuit of the right long-term policy.
http://www.tonyblairoffice.org/news/entry/tony-blair-urges-uk-to-shape-the-future-of-europe/.
He is a far better presenter than Kenneth Clarke.
His role in the Iraq war is clear for all to see but if Mrs May were in his place, would she have said no to a US President?