The Ontario election campaign isn't even two weeks old and already everything has changed.

From a wide double-digit lead in the polls, Doug Ford's Progressive Conservatives are now ahead by only four points in the CBC's Ontario Poll Tracker.

Andrea Horwath's New Democrats, meanwhile, have made gains in poll after poll — and according to two recent polls may have moved into an effective tie with the PCs.

The Poll Tracker, an aggregation of all publicly available polling data, puts the PCs at 37.9 per cent support, with the NDP behind at 33.8 per cent. That represents a gain of over seven points for the New Democrats since the last pre-campaign update.

Those gains have come from both the PCs and the Liberals. The two parties have slipped three points each since the beginning of the campaign, with Kathleen Wynne's Liberals now down to 23 per cent. The Greens under Mike Schreiner stand at four per cent support in the Poll Tracker, largely unchanged.

Rick Anderson, Catherine Cullen, Susan Smith and Francoise Boivin discuss recent polls showing Andrea Horwath's NDP gaining on Doug Ford's Progressive Conservatives. 11:18

Two of the three polls published recently show that the gap between the PCs and the NDP has narrowed even further. In a survey conducted online between May 16 and 18, Abacus Data put the PC lead at just one point. A more recent online survey by Ipsos/Global News (May 18-21) puts the New Democrats ahead by one point — the first poll in three years by any pollster to put the Ontario NDP in first place.

Another survey by Mainstreet Research (May 15-18) showed only modest gains for the New Democrats and the PCs still ahead by about 13 points.

Nevertheless, while the margin between the two parties may be up for debate, every poll published in this campaign so far has shown the NDP making progress.

They also show that the underlying trends are pointing in the NDP's favour. A survey by the Innovative Research Group showed that in the opening days of the campaign, nearly everything that voters were hearing about Horwath improved their opinion of her — while almost everything they heard about Wynne and Ford had the opposite effect on them.

PCs still hold the edge in seats

If an election were held today, the PCs would still have a 85 per cent chance of securing a majority of the seats up for grabs. The Poll Tracker estimates they would win between 51 and 88 seats, straddling the 63 needed for a majority government. But most scenarios still end with them over that threshold, and the most likely outcome is somewhere around 75 seats for the PCs.

The NDP would win between 30 and 59 seats, with the 44 seats in the projection model being the party's best performance since it formed government in 1990 — and the second-best result in its history.

The Liberals, with between zero and 26 seats, are on the ropes. The popularity of a few local MPPs may be the party's saving grace at this stage.

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But the silver lining for Wynne is that the Liberals' descent appears to be slowing as the party approaches what could be its floor. In the past week, the Liberals have slipped less than a point, while the PCs have dropped three.

There is little more to be gained by the New Democrats if the Liberals drop further behind. Instead, they need to start taking support away from Ford. Because of how the PCs' support is distributed, the New Democrats might need a province-wide lead of as much as four points to have a good shot at winning the most seats.

Andrea Horwath is not there yet and the PCs retain some important structural advantages. But if Doug Ford is unable to put a halt to the NDP's forward momentum, Horwath has enough time to get there by June 7.