The CBC Pollcast, hosted by CBC poll analyst Éric Grenier, explores the world of electoral politics, political polls and the trends they reveal.

The Liberals won three of four federal byelections on Monday, retaining two of the seats they had previously held and taking a third that had been a Conservative stronghold.

Though Prime Minister Justin Trudeau has dealt Conservative Leader Andrew Scheer his second byelection defeat in less than two months, it was not all good news for the Liberals or bad news for Scheer.

Despite the Liberals' breakthrough in the B.C. riding of South Surrey–White Rock, which the Conservatives had held since the 1970s, the party saw its vote share drop by an average of 3.8 points across the four byelections. The Conservative vote share increased by an average of 5.5 points.

But will Scheer's second defeat raise questions about the direction he is taking the party, whose leadership he assumed earlier this spring? What do the results mean for the NDP's Jagmeet Singh, who has been in the job for little more than two months, after his party's support dropped across the board? And what does the Liberals' dipping support outside of South Surrey–White Rock mean for their prospects in 2019?

To break down the results of Monday's four federal byelections in South Surrey–White Rock, Battlefords–Lloydminster in Saskatchewan, Scarborough–Agincourt in Ontario and Bonavista–Burin–Trinity in Newfoundland and Labrador, Pollcast host Éric Grenier is joined by the CBC's Aaron Wherry.

Listen to the full discussion above — or subscribe to the CBC Pollcast and listen to past episodes.​

Follow Éric Grenier and Aaron Wherry on Twitter.