this is what happened in 2008, when dion was running:

liberals: -4%
greens: +2.5%
conservatives: +1.5%
ndp +.5%
bloc: -0.5%

turnout: -6%

result: conservative minority government. and, they should have lost power, due to losing confidence of the house.

you can balance out any marginal conservative increases by observing the decrease in turnout. what actually happened was that the liberals lost a lot of support to parties on their left.

so, don't believe these tory revisionists that want to rewrite history. dion was fighting off a leftist resurgence, and had to compromise, or the outcome would have been worse.

(source: https://en.wikipedia.org/wiki/2008_Canadian_federal_election)

and, in fact, we did the experiment - the next guy swung very, very hard to the right, and what happened?

this was the result of the 2011 election, after dion had been replaced by the much more right-wing ignatieff:

liberals: -7.5%
ndp: + 12.5%
bloc: -4%
greens: -3%
conservatives: +2%

turnout: + 2%.
note: there were substantive accusations of vote-rigging by the conservative party in this election.

result: conservative majority government. the liberals ended up in third place, behind the ndp.

so, we see what happens when the liberals swing to the right - they bleed dramatically to the left. in 2015, trudeau ran more like dion than ignatieff, and it finally paid off. there's an argument that trudeau would not have won had dion not set the groundwork for it. but, the basic fact is that people voted to get rid of harper, and saw trudeau as the more left-leaning option on the table. in 2019, that bleed is moving towards the greens rather than the ndp as a consequence of factors that are outside of the liberal party's control, but we're seeing the same basic pattern emerge, as the liberals move right, yet again.

and, if the greens get a huge bump, they could very well throw trudeau right out of office.

i think the data is in fact pretty clear - had dion run as ignatieff, he would have had the same results as ignatieff. and, trudeau's abandonment of the left will likewise leave his party decimated, in the end.