Andrew Scheer is arguably doing much worse than Jagmeet Singh. However, the vast majority of the Canadian punditocracy is conservative so that view hardly ever gets expressed.
The Conservatives are doing better in the polls than the result they received during the 2015 election, while the NDP is, at best, only doing as well (not a huge amount of difference either way) however I think the Conservatives are doing so in a way that could rebound on them negatively. They are clearly playing up fears over the irregular crossings and I think Scheer leaves himself open to charges that he is a dishonest fear monger. Impossible to know how these things will work out, but this isn't the first time that Scheer has gone for short term gain at the possible expense of his longer term prospects.
I think Scheer will have difficulty catching on in the GTA and Greater Vancouver. Running up the margins in the Prairies and rural Ontario won't translate into many seats.
The NDP will almost certainly lose ground in Quebec, but there may be an opening for Singh among progressives in Ontario and BC as well as in the Sikh community. But he's not running "for PM."