The one person who will be relieved at tonight's 1 News Colmar Brunton poll is National leader Simon Bridges, but only slightly.

He and plenty of others would have been expecting a far worse result than this poll which has National falling by two points to 40 per cent and Labour rising by three points to 48 per cent in the past two months.

That does not mean that Bridges' leadership is secure.

But it has not sunk so low that it would force a leadership change yet.

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And no one would launch a coup on the back of a national tragedy which undoubtedly has had an impact on the polls.

The Christchurch mosque massacres set a test for Prime Minister Jacinda Ardern which she passed effortlessly and selflessly.

She united the country by turning global grief into a sense of unity.

So outstanding was her leadership it would have been unbelievable if that had not been reflected in a poll conducted so close to the event.

The slight surprise is that Ardern is not even higher than 51 per cent as preferred Prime Minister compared with Bridges' 5 per cent.

She rose by seven points and he dropped one, as did front bencher Judith Collins.

The gap between Ardern's popularity and Bridges' was huge before, and it is huge now. That is never going to change.

The gap between the two parties, however, is more important, and more troubling for National.

It was small before (three points in February with Labour on 45 per cent and National on 42 per cent) and is large now (eight points with Labour on 48 per cent and National on 40 per cent.

The worry for National is that trend continues.

With growing disquiet within National over some of Bridges' judgments being aired more publicly, most recently the employment dispute his office has with a press secretary, and the supposed inquiry into the party's culture, it is easy to see that trend continuing.

The Government is poised to announce its decision on a capital gains tax within the next two weeks and deliver its second Budget at the end of next month.

Both are opportunities for the Government to consolidate its popularity.