Ontario

The problem as I see it is that both the OLP and the ONDP see the other as "taking their voters". "If only those idiots supporting the would vote for us, then we could defeat Doug Ford!"

Meanwhile, if they ran as a semi-coalition, and got out of each others way in a few dozen ridings, they could at least reduce Ford to a minority, or possibly form a coalition. In the absence of proportional representation or a ranked ballot (or both), it's the best way to prevent vote splitting among 60% of Ontario from allowing Ford to win again.

Examples:

• Scarborough Centre: If the NDP gets out of the way, it goes from Lean PCPO to Likely OLP
• Timiskaming-Cochrane: If the Liberals get out of the way, Lean PCPO → Lean NDP
• Algoma-Mnitoulin: Liberals get out of the way, Toss-up NDP/PCPO → Lean NDP
• Barrie—Springwater—Oro-Medonte: NDP get out of the way, Toss-up OLP/PCPO → ... okay this one probably stays a toss-up, but the advantage shifts to the OLP from the PCPO.

Notably, I would leave ridings like Humber River—Black Creek out of consideration, as that's a solid 3-way race.

If you're concerned about being able to govern as a coalition, make your #1 priority electoral reform. Get that done and then see where it goes from there.

I took 5 minutes, and looked at one polling aggregator, and found a possible path to moving 4 seats. You need to move ~30 seats to get Ford out of power according to today's polling. If the OLP and ONDP can't work together to find a path to victory for them together, neither of them deserve to lead, IMO.

(Fortunately for me, I get to vote for Catherine Fife (NDP-Waterloo), and her seat is pretty safe)