First, the poll results reflect a poll taken in February. So one has to acknowledge that opinions and attitudes are fluid. Very possible there may be a bit of change in the numbers were this poll taken again this month or next. In the same vein, I wouldn’t build my house on what any party has “already ran on.” It is April, not November.
Secondly, it appears that the 20% of voters that currently perceive immigration as the biggest issue in the upcoming election is being overlooked on the whole of the results. If one in five already consider this as the biggest issue, that is a problem for any candidate. Additionally, as stated in the article, this same poll was also conducted in December and at that point in time immigration being cited as the top issue was only 13%. So, the suggestion here is that the immigration issue is a growing concern.