The moderate left is losing everywhere. This is partly because of the populist right, which has captured working-class voters by opposing free trade and immigration. But mostly, the moderate left is losing to the radical left, which has usurped the mantle of change and harnessed the indignation of a new generation of voters.

From France's Jean-Luc Mélenchon and Spain's Pablo Iglesias to Bernie Sanders in the United States and Jeremy Corbyn in Britain, the global left's new leading lights don't preach incremental change. They talk about overthrowing the existing order with the zeal of true revolutionaries.

The revolutionary talk still repels more voters than it attracts, though the Corbyn-led Labour Party has defied the pundits by performing better than expected in polls leading up Britain's June 8 election. Still, where the radical left has created new political parties, such as in France and Spain, the result has been the decimation of the centre-left Socialists in both countries.

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Mr. Mélenchon's powerful showing in the first round of France's recent presidential election, capturing 19 per cent of the vote and outpolling his Socialist rival by a margin of 3-to-1, was greeted with joy and trepidation in Quebec, a province whose politics has often taken on a European accent. In short, Mélenchonmania has infused new energy into the radical left Québec Solidaire (QS). For the Parti Québécois, however, it is one more nail hovering over its steadily closing coffin.

PQ Leader Jean-François Lisée initially took an if-you-can't-beat-them attitude, proposing an alliance with QS, which now holds a trio of Montreal ridings that used to be PQ strongholds and has eaten into PQ support enough to deny it victory in at least a dozen more across of the province. The proposed arrangement, formally known as la convergence, would have seen each of the two nominally sovereigntist parties refrain from running a candidate in selected ridings where competing against the other would allow the Liberals or the right-leaning Coalition Avenir Québec (CAQ) to slip up the middle.

For weeks, QS leaders publicly kept the door open to a pact with the PQ. That is, until a special congress held May 21 to debate la convergence, when QS members told them what they thought of the idea. "For racialized communities," QS activist Dalila Awada told the meeting, the PQ embodies "twin beasts" of "neoliberalism and racism." She sounded polite, compared with many others who spoke up.

PQ's proposed Charter of Quebec Values, which would have banned public-sector employees from wearing "ostentatious" religious symbols such as the hijab, continues to the haunt the party. For Québec Solidaire, which has sought to make inroads among immigrants, the identity politics to which the PQ's aging membership clings has made it toxic and passé.

Mr. Lisée did not take kindly to the rejection. Instead of making eyes at QS leaders, he now gives them the evil eye. First, he compared them with the Politburo in the former Soviet Union for sabotaging his convergence proposal. Then he called QS's newest MNA – Gabriel Nadeau-Dubois, the charismatic former student leader who this week won a by-election in a Montreal riding adjacent to Mr. Lisée's – an "objective ally of the Liberal Party" for dividing the left.

To be fair, QS has often struggled to articulate a coherent message. The party officially considers sovereignty a precondition to the environmental and economic revolution it seeks to unleash. But it has played down its separatist leanings as it seeks to woo more young, ethnic and anglophone voters, even reneging its signature on a separate agreement with the PQ on a "road map" for sovereignty.

Still, the biggest loser amid all this mud-throwing remains the PQ. It is not just hitting historic lows in the polls, but has been replaced as the first choice among francophone voters by the Coalition Avenir Québec. It seems Mr. Lisée's promise not to hold a referendum during the first mandate of a future PQ government has freed federalists unhappy with the Liberals to shift their support to the CAQ, which has played the identity card to eat into PQ support outside Montreal.

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Mr. Lisée, meanwhile, keeps insisting the PQ offers a progressive social-democratic alternative to the tax cuts and austerity practised by the Liberals and promised by the CAQ. But he keeps on alienating progressive voters with a dog-whistle discourse on immigration.

The next election is still far enough off that anything could happen. But as QS rises under Mr. Nadeau-Dubois, who resembles a younger and more telegenic version of Mr. Mélenchon, the PQ is in mortal danger. Mr. Nadeau-Dubois could do to it what Mr. Mélenchon has done to France's Socialists.