I find that people frequently misunderstand what a Portillo moment is. It isn't just 'someone high profile losing their seat' - there were plenty of those in 1997 and in every election since.
There are two elements to it - first it needs to be some so high profile that their absence from parliament fundamentally shifts the future of their party. Portillo losing his seat meant he couldn't run for the leadership of the Tory party for instance. Second, it needs to be completely unexpected. Saying 'I think x is a candidate for a Portillo moment' means that x cannot be a Portillo moment, because you expect it as a possibility. The real Portillo moment would be y losing their seat that nobody thought was even remotely likely to flip.
Therefore, Boris or Raab can't be Portillo moments this election because it's now fairly common knowledge their seats are at least somewhat vulnerable. If Corbyn or Patel lost, then that would be a Portillo moment. Of course, neither of them would lose in a trillion years, but you get the point...
Probably the closest recent examples we've had here in the States came from the 2018 midterms. Though the Democrats were expected to flip the House, they also picked up a few seats that were considered pretty safely Republican. To me, the biggest surprise of the night was Kendra Horn (OK-05), a Democrat who won in an R+10 district 50.7-49.3. The poll taken closest to election night predicted that incumbent Steve Russell (R) would win by twelve points.
Mind you, it doesn't necessarily qualify in full as this flip didn't change the political landscape.
Eric Cantor losing his primary when he was next in line to be Speaker after Boehner seems closer. Very few saw it coming and it impacted the House leadership. It wasn't during a national election though, so that might disqualify it.
