Apparently because most of the Country are anti-Tory that means there is a "progressive majority", forgetting of course the anti-Labour, anti-Liberal minorities are smaller than the anti-Tory one at the moment.
The Idea that the "progressive Left" are One thing is laughable, they are as fragmented and divided as the "Right", but the difference between "left and right" is that the so called Progressives believe that the future can be planned, when you believe you have the truth, then its very hard to form coalitions and alliances that deflect from that "truth"
By Contrast the "right" who are equally divided don't believe in utopias, so you dont plan for one. The Conservative political philosophy generally says that human beings are flawed and as such the systems we create are flawed, society and the economy are reflections of the flaws human beings exhibit. Thus pragmatism is at the core of Conservatism, you do the best you can in the era that you find yourself, so the "rights" coalition is much stronger through a looser ideological message, in so far as any light ideology needed relating current political thinking of the time.