When provincial NDP leader Andrea Horwath extracted progressive concessions from Ontario's Liberal premier, Dalton McGuinty, as the price of preserving his government this week, she not only avoided an election but also underlined the very real differences between the two parties.
Horwath has boldly secured a tax on the super-rich, soft-pedalled by the Libs as a surtax, a seemingly radical move supported by the vast majority of Canadians, though only reluctantly by McGuinty.
She's managed to put the notion of reasonable taxation back in discussion at a time when the Liberals provincially are trying to position themselves as Slash-and-Burn Lite while in fact cutting like the Conservatives federally - except where restrained by the NDP. As Harper's Conservatives come under fire for outrageously over-budget spending on unnecessary fighter planes, the Liberals simply call for open bids.
The NDP says forget the weapons of mass budget destruction altogether and use the money for social programs, hospitals and education. Two vastly different approaches for parties too quickly lumped together by progressives.
The political shape-shifting is taking place federally as well. The Liberals are scrambling to dance in the disappearing middle when a clear division between Canadians is firming up along Conservative and NDP lines.
The same week that federal NDP leader Thomas Mulcair and his family moved into Stornoway, official residence of the leader of the opposition, former Liberal PM Jean Chretien publicly daydreamed about merging the two parties, to the horror of interim Lib leader Bob Rae.
The cagey Chretien is continuing a Liberal tradition of eating its own, fouling the waters for the struggling Rae.
Meanwhile, Mulcair and his party continue to challenge or top the Conservatives in national public opinion polls, clobbering both the Liberals and Conservatives in all-important Quebec.
While Chrétien and the old guard might dream of life support being offered the badly listing Liberals by a merger with the NDP, progressive Canadians are seeing a clarity of choice - that the best way to realize Chretien's dream of defeating Harper is by uniting behind the NDP and using the next three years to build and shape that party from within.
That includes the Greens. Elizabeth May's party should hold one more convention - one of dissolution - so this political vanity enterprise can stop robbing progressive votes in its hopeless attempt to build another non-Conservative party.
The NDP has the greatest chance in a generation of taking federal power. It is the only party committed to electoral reform - the kind that makes room for all varieties of protest parties without ensuring perpetual Conservative majority rule with a minority of votes.
All those who want electoral reform should join the NDP and build it to achieve truly representative democracy in Canada. The Liberals never did it; the Conservatives won't. Only the NDP is committed to acting on this long-overdue initiative.
As the NDP demonstrates that it won't run from victory but instead will run for it, the party emerges as the best bet for creating real progressive change.
A vote-bleeding Green party is pointless. And as NDP and Liberal differences are continually and critically underlined, progressive Libs should stop waiting around for unlikely mergers. They should build the future from within the NDP so they can help shape the next Canadian federal government.