As the Brexit deadline approaches, I've seen reporting recently over the British government using participation in the European Parliament elections as a threat to convince MPs to not force the government to seek a lengthy extension. For example, this snippet from a Bloomberg article (emphasis is their heading):
Govt Doubles Down on MEP Election Threat (12:15 p.m.)
Speaking to reporters, May’s spokesman James Slack also hardened the government’s language about the likelihood of a longer Brexit extension leading to the U.K. holding EU parliament elections.
“If we’re unable to win a meaningful vote this week, then the prime minister will have to seek a longer extension. That will inevitably involve participation in European parliamentary elections.”
As someone not from Europe, I am uncertain why this is a viable threat to get MPs in line? I understand from What would a delayed Brexit mean for the 2019 European Parliament election? that the process might be messy (almost regardless of what the UK Parliament does it seems), but what in particular makes participation in the MEP Election so disconcerting to MPs that it could be construed as a threat, rather than a inconvenience to be put up with until the final Brexit agreement is settled upon?