I’m going to challenge some of your facts, Fred-Rick.
Canada has had at least three parties since the 1920s. In particular, the CCF Party started speaking for the working people, got a few seats in Parliament, and attained a platform. This party — now known as the NDP — has maintained a 15 to 50 seat presence ever since. They have not come close to winning a national election, but they have taken quite a few provincial elections over the years.
They have forced the Liberal Party to the political left. There is always a little battle between these two parties for the left wing vote. The Liberals seem to be more successful, but the NDP still finds a political voice which then prevents the Liberals from going to the right. Right now, the Liberals are in a minority government and know the NDP can send the Liberals back to the polls at any time. An interesting check-and-balance.
I really can’t explain why our Westminster system has not eventually forced the NDP out of the picture, giving a Canada a two-party state. This is, to me, is the natural outcome of Westminster, but the NDP has defied these odds for almost a century.
The success of the UK Liberal Democrats in 2010 and a minority UK government gave the LD’s leverage they never had before. To form a coalition, they made a bargain with governing party to hold a referendum on a new electoral structure. In my opinion, this new structure would have made UK more democratic. And it would have given the LD a bigger presence is UK parliament, more in line with their popular vote. The Labour and Conservatives would have been losers. Of course, the two bigger parties did not want this referendum to succeed, but it was up to the British people, not the parties.
And the referendum was soundly defeated. It seemed the British people wanted a two-party state. Today the LD’s are an insignificant player in British politics.
I cannot explain this loss of that UK referundum.
Here is teh Wiki article: https://en.wikipedia.org/wiki/2011_United_Kingdom_Alternative_Vote_referendum
In a like manner, the province of British Columbia had three referenda in the 16 years to reform its Westminster system to a model more in line with PR. Even the major political parties want this change. Yet the citizens soundly chose to go back to the 1867 model. Then next election, they will complain why the popular vote is so lopsided with the parliamentary seats allocated to each party. I cannot explain their thinking.
Is their hope for a third party in the US? I would say there is. Half of registered Americans do not vote in any election. They can make third parties viable.