The difference is enough to ensure success or failure in the vital Commons vote that must accompany the Government's review.
In a free Commons vote, PR would surely be defeated.
It would surely be unthinkable (but not unusual) for them to side with the Government when it comes to the Commons vote.
The House of Commons votes to approve an education reform bill.
The House of Commons votes on two crucial budget bills.
In the event, he passed up that chance and was forced to call an election in March 1979 when he lost a Commons vote.
If he'd struck a deal, that would have meant a new treaty, entailing a Commons vote and, given his past promises, a referendum.
"I cannot assume how they would vote when it comes to a Commons vote, but I am talking of more than 30," she said.
Other countries treat the issue as a nonpartisan one; in Britain the House of Commons votes on it without party positions.
It was defeated in a Commons vote by a margin of 4:1.