https://www.bbc.co.uk/news/uk-politics-46416591
Labour are suggesting that they'll call a no confidence vote in the Government if the Brexit deal vote is lost by the Government.
"Under the Fixed Term Parliaments Act, if the government loses a vote on a motion of no confidence it has 14 days to pass a second confidence motion, or Parliament is dissolved and a general election is called."
I reckon this could backfire and swing MPs behind the Government deal.