The NDP is up in the polls ... and Doug Ford has noticed

Today the Ontario party leaders square off for the second time this week, but this time it's in Parry Sound for the Northern Leaders Debate.

The NDP is feeling good after a big thumbs up from the elementary teachers' union, while the Liberals are facing possible defeat in a southwestern Ontario riding long a considered a Grit stronghold. 

Here's where we are on day three:

Headlines:

• Northern voters get chance to grill Ontario party leaders at morning debate | This is the second leaders debate and CBC is live streaming and live blogging it here. 

• Ontario aims to tame the 'Wild West' of 3rd party election advertising | CBC's Mike Wise looks into the grey areas when it comes to third-party spending and political ads on Faceook

• ​Despite promises, Ford unlikely to release fully costed PC platform | CBC's Joanne Chianello does the math on Doug Ford's promises.

The Moment:

Throughout the campaign, PC Leader Doug Ford has been laser focused on his Liberal rival. That all changed this morning in Parry Sound.

Speaking to reporters, Ford opened up a second front — shifting his attention to Horwath. After all, the NDP is the major political player in many northern communities and recent polls suggest the party may be running second only to the PCs among voters. 

• Andrea Horwath's NDP making gains as Ontario election begins

"Just who is the real NDP?" Ford said. "Once upon a time, the NDP claimed to fight for the working people up here in the north or in our factory towns. But over time we've seen the growth of a second NDP: a group of downtown Toronto special interests who hold radical — and I mean radical — ideologies," Ford continued. 

He went on to suggest that the NDP would scuttle resource development projects.

"The NDP will turn its back on northern Ontario."

Ford fired the volley one day after Horwath and her NDP secured an endorsement from the politically influential union that represents public elementary school teachers in the province.

CBC's Poll Tracker shows the NDP is gaining momentum and now sits second at 27.2 per cent, but the party is still well behind the PCs, who sit at 41.1 per cent.

• CBC Poll Tracker | Get the latest projections here

Riding to Watch:

Essex, Population: 125,440, profile by Katera Zappacosta 

This riding was once a Liberal stronghold, but this time around it doesn't even have a Liberal candidate. At least not yet.

"We'll have more to say in the near future," says a Liberal party volunteer.

Essex is part of a larger story playing out in southwestern Ontario — one of three ridings that have yet to nominate a Liberal candidate (Lambton-Kent-Middlesex and Sarnia-Lambton).

• Will a 'PC blue wave' sweep over an orange Windsor-Essex?

The NDP's Taras Natyshak won a second term in 2014 with 60 per cent of the vote.

Now, he's up against PC party newcomer Chris Lewis. The former firefighter and Kingsville town councillor tells CBC that people who've voted Liberal in the past are coming into his office for signs.

The Conservative support shouldn't be too much of a surprise — federally, it held the riding from 2004 to 2015.

Where the leaders are:

• Ford: Northern Leaders Debate in Parry Sound (11:30 a.m.), Meet and Greet (1 p.m.), Visit in Tay Township (4:30 p.m.), Rally in Barrie (6:00 p.m.)
• Horwath: Northern Leaders Debate in Parry Sound (11:30 a.m.), Event in Sudbury (4:30 p.m.)
• Schreiner: Morning events in London, Campaigning in Guelph (2 p.m.), 
• Wynne: Northern Leaders Debate in Parry Sound (11:30 a.m.)

For more Ontario election coverage:

• Ontario Poll Tracker | The latest projections
• Vote Compass | See how your views compare with the party platforms
• Complete election coverage | Links to all our coverage
• Help CBC track political ads on Facebook | Learn how here