Nik Nanos is The Globe and Mail's pollster and the executive chairman of Nanos Research.

Going into the U.K. election, the lead of Theresa May's Conservatives was called unassailable. With a 21-point advantage on the first day of the campaign, the pundits and the strategists were preparing for a majority that would have an estimated 100-seat cushion.

A funny thing happened, however. It's called an election. That 21-point advantage evaporated to a two-point win and along with it a governing party majority. Now the Conservatives are propped up by the Democratic Unionist Party.

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The Trudeau Liberals should take note. Their sunny ways and prolonged honeymoon are about as solid as Ms. May's 21-point advantage at the beginning of the U.K. election. The latest Nanos tracking has the Liberal double-digit advantage turning into a single-digit advantage. Indeed, Liberal support last week was the lowest since before the last federal election. The good news for the Liberals is that they still enjoy a comfortable lead over the Conservatives and their newly minted leader Andrew Scheer. The bad news is that the second half of their mandate poses more political risks to manage.

This fall, the Liberals will approach the halfway point of their mandate and the election clock starts ticking downward closer to voting day.

For the first part of their mandate, the Liberals will be able to say they have delivered on a more positive and open style of government, at least compared with Stephen Harper. They welcomed more than 30,000 Syrian refugees, moved forward on their environmental agenda, advanced assisted dying, appointed more independent-minded senators and looked to legalize marijuana. The deficit was larger than promised but their priority was to invest in infrastructure, and at the same time, they managed to come to agreement with the provinces on health care (except Manitoba).

There are a series of risks that loom large.

First, managing the Trump administration and the renegotiation of the North American free-trade agreement will take a very deft hand and also some luck. The bipartisan strategy of including former Progressive Conservative prime minister Brian Mulroney is a very good step but Canada is hostage to the whims (and tweets) of President Donald Trump.

Negotiating a new and improved NAFTA 2.0 would be a win for the government. The challenge will be engaging a President distracted by other domestic and international priorities and also moving forward in a timely manner, hopefully ahead of the Mexican election in July, 2018, which could very well be gripped by a populist anti-Trump sentiment. NAFTA negotiations going sideways because of either the U.S. administration, a delayed timeline or a volatile Mexican election will have political repercussions at home as a fragile economic mood becomes even more uncertain.

Second, although the Liberals have delivered on a number of promises, it was their big promise to make things better for the middle class that may be their most daunting task. Where the Harper Conservatives embraced bespoke tax breaks for segments of voters, the Liberals have promised to raise the fortunes of all (except the top 1 per cent of income earners). This is a promise of the first magnitude and the most important promise made by the Trudeau Liberals during the election. Issues such as assisted dying, legalizing marijuana and an independent Senate are generally second-magnitude issues. Canadians take an interest and have views but they do not pack the same political punch as "Do I have a job? Can I make a living wage? Where are the jobs for my children?"

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Third, the winning Liberal coalition that propelled them into government is fraying at the edges. The party's numbers are dropping in the province of British Columbia because of the dual track of approving a pipeline and moving forward on carbon pricing. Although some might not have noticed, the Bloc Quebecois is regaining strength in Quebec. This with a BQ leader, Martine Ouellet, still transitioning from the National Assembly in Quebec to Ottawa. Looking beneath the numbers, the Liberals' support among younger middle-aged Canadians is sliding and now tied with the Conservatives.

This pollster agrees with those who say the most important poll is the one on election day. However, leading up to election day gives a sense of the risks and opportunities for all the parties. The data suggest that the cloudless sunny ways are over. Sure, some days will be better than others for the Liberals. Now, reality will set in as more Canadians focus on what the Liberals have done to make things better for that large swath of Canadians who consider themselves part of the middle class.