A new poll suggests that federally the Conservatives aren't closing the gap on the Liberals as summer begins.

The Nanos survey conducted in mid-June, after the House of Commons had wrapped for the summer, suggests the Liberals had support of 34.2 per cent of 816 committed voters, down 1.2 percentage points from an early April survey.

Support for the Conservatives dropped 1.9 percentage points in those two months, from 31.3 per cent of committed voters to 29.4 per cent.

The New Democrats gained almost two full percentage points in support from survey to survey, up 1.7 points from 23.6 per cent to 25.3 per cent.

However, the Official Opposition in the House of Commons continues to sit in third place, displaced again by the Liberals as the top-ranked alternative to the governing Conservatives.

The numbers are considered accurate within 3.5 percentage points, 19 times out of 20.

The Liberal lead of 4.8 percentage points over the Conservatives in this poll is beyond the margin of error and up from the 4.1 percentage point lead in April's survey.

Before April's poll, the Liberals hadn't led a Nanos survey since the spring of 2009.

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"I would say the change is a factor of a number of things … it is the expense scandal, the election of Justin Trudeau and also the malaise in the economy," said Nik Nanos, president and CEO of Nanos Research.

"Roll those three things up and it provides for a very difficult environment for the Conservatives politically."

‘Grumpy former Conservatives’

Nik Nanos goes beyond the numbers every Wednesday on CBC News Network's Power & Politics with host Evan Solomon. (Nanos Research)

The Green Party saw the biggest gain in this poll, up to 6.4 per cent support from 4.2 per cent.

Bloc Québécois support dipped from 4.8 per cent to 3.7 per cent.

The number of respondents who said they were undecided rose from 11.2 per cent in April to 18.4 per cent in June.

"A significant portion of those new undecided are probably former Conservatives; people don’t usually switch from one political tribe to another overnight, they kind of move into the undecided category," Nanos said.

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"It’s important to re-convert those undecided voters, what I’ll call ‘grumpy former Conservatives,’ out of the undecided column back into the Conservative category."

These results came from a random national telephone survey of 1,000 Canadians age 18 and older held between June 16 and June 19. The margin of error for the survey is 3.5 percentage points 19 times out of 20.