Donald Trump gets a convention bump, but Hillary Clinton's could be next

Thanks to a bump from the Republican National Convention, Donald Trump has closed the gap on Hillary Clinton in U.S. polls. But with the Democratic National Convention now in full swing, will Clinton find herself comfortably in the lead again this time next week?

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According to the CBC's new Presidential Poll Tracker, which you can follow throughout the campaign to see where the race to the White House stands, Clinton retains a narrow lead with 44.6 per cent to Trump's 42.8 per cent in a weighted average of polls.

Since the convention got underway, this represents a drop of 0.4 points for Clinton and a gain of 1.8 points for Trump.

Support for other candidates, including the Libertarians' Gary Johnson and the Green Party's Jill Stein, is averaging 12.6 per cent, a drop of 1.4 points since July 17.

But the Poll Tracker (full methodology) takes into account a large number of polls stretching back further than the end of last week's convention, in order to prevent it from bouncing around dramatically from one poll to the next. Looking at just those polls that have been conducted after Trump's convention speech on Thursday, the Republican nominee has averaged 45 per cent support among decided voters, compared with 43 per cent for Clinton.

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Compared with where he stood in polls taken in the three days before the Republican convention began, this suggests that the Republican shindig in Cleveland boosted Trump by about four points among decided voters.

Clinton ahead in the swing states — barely

While this has put Trump in a better position in the electoral college, he still trails Clinton on this measure. The Democratic nominee is projected to win 347 electoral college votes if the election were held today, based on national and state-level polling. Trump is projected to win the remaining 191 votes.

But a number of states are very close. Taking into account those states currently considered to be close, Clinton's likely range of electoral college votes stands at 259 to 347, while Trump's sits at 191 to 279.

A total of 270 electoral college votes is needed to win.

Clinton is leading several of these close states by tiny margins: 0.8 points in Iowa, 0.6 points in North Carolina, 0.5 points in Ohio, and just 0.1 point in Florida. If those states were flipped over to Trump — and a gust of wind could do that at this point — the electoral college vote would sit at 279 for Clinton and 259 for Trump.

Trump is further behind in Pennsylvania, where Clinton leads by 2.1 points. 

Scroll to the bottom of this article for a full state-by-state breakdown of the electoral college map.

A conventional convention bump?

That Trump's poll numbers have improved in the wake of the Republican convention should come as no surprise. Since the 1960s, conventions have delivered bumps to the party nominees in almost every election year, though the size of that bump can vary significantly. It has averaged about two points in recent years (but six or seven points prior to 2004), making Trump's convention bump typical.

If Clinton benefits from a similar bump this week, she will find herself more comfortably ahead of Trump once again as the polls reset themselves to pre-convention levels.

But the Republican convention may have had a more long-term positive impact on one of Trump's most troublesome problems: whether people like him or not to begin with.

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Trump and Clinton are the two most unpopular presidential candidates in modern history. Until now, however, Clinton had the advantage that she was only the second most unpopular candidate. 

Polls taken since Trump's speech at the convention, however, have suggested significant increases in his favourability ratings. An average of four polls (by YouGov, CBS, CNN and Morning Consult) suggests his favourability has improved by a little over four points while his unfavourability has dropped by an average of four points.

Across those four polls, Trump's favourability now stands at an average of 38.5 per cent to 55 per cent unfavourable. Bad numbers, but Clinton's are worse: 37 per cent favourable to 57 per cent unfavourable.

She will need the Democratic National Convention to do the same thing that the Republican gathering did for Trump if she is to get back on track. But if Clinton doesn't get a bump of her own out of the Democratic convention this week, Trump may become the favourite to become America's next president.

The Presidential Poll Tracker includes all published mainstream surveys, a list of which can be found here. The polls are weighted by sample size and date, as well as the reliability of each pollster as rated by FiveThirtyEight.com. The electoral college is projected by applying the same weighting standards to state-level polls and combining this with a uniform swing model, based on how the current national polling average compares with the 2012 presidential election. Surveys included in the model vary in terms of sample size and methodology and have not been individually verified by the CBC. A full methodological explanation can be found here.