With 4 by-elections now seemingly coming up, now seems as good a time as any to take a look at each riding.
New Westminster – Coquitlam
Located on the edge of greater Vancouver, the riding is a traditionally a swing riding between the NDP and the PC's/Reform/Alliance/Conservatives, (the Liberals haven't won in the area that makes up the riding since the 1968 Trudeau victory) although the Liberals have occasionally made it a 3 way race when the vote has split since then, finishing close thirds in 1993, 1997 and 2004. The Liberal vote collapsed last election, going from 23.5% and 11,931 votes in 2006 to 11.3% and 5,615 votes in 2008. The riding has been often been a person battle between Dawn Black from the NDP and Paul Forseth from the Conservatives, facing each other in 2006, 1997, and 1993. On paper, this is the Liberals best chance of winning one of the 4 by-elections, although that isn't saying much, a more realistic goal would be lifting the Liberal vote from the lows of the 2008 results into the mid-20% range that the party usually turns in when it is perfoming normally. From all I have heard, Fin Donnelly was a good choice for NDP candidate, as the riding is often split between the more NDP friendly New Westminster and the more Tory Coquitlam, and Donnelly was a fairly popular Coquitlam councilor, so in addition to the normal NW NDP vote that helped Dawn Black, he can probably have a personal vote in Coquitlam. The Liberals should, as I said, focus on simply trying to reach say, 25% to show they are back on their feet in the ridings, and should in particular try to work on getting Green voters to go Liberal.
(I didn't do it deliberately, but this result would basically mirror the 2006 result)
Cumberland – Colchester – Musquodoboit Valley
The NDP has high hopes for this rural Nova Scotia riding, vacated by former Tory Bill Casey. They are still hoping to ride the wave created by the provincial party's victory in the most recent provincial election, in which the NS NDP won 3 of the 5 provincial ridings in CCMV, and if the combined total of all those ridings were combined, it would produce an NDP victory. I think though, that the Tories should hold this one. Conservative candidate Scott Armstrong was a middle-man between Casey and the federal Conservatives, and is respected by both Casey loyalists and Tory diehards, so he should be able to pull out most of the old Tory vote for himself. The riding has a very long Tory history, with Casey's election as an independent, and the 1993 PC wipeout (in which Casey lost the seat) being the only times the riding has voted anything but Conservative since 1957 (and even prior to that, the seat leaned Conservative, going all the way back to Father of Confederation Charles Tupper). I expect a Tory victory with the NDP a strong second, and the Liberals making up some of the ground they lost in 2008.
Montmagny – L'Islet – Kamouraska – Rivière-du-Loup
Held by the BQ since 1993, the Conservatives had hoped that the Mario Dumont effect would deliver this seat to them as part of the Quebec breakthrough that would yield a Tory majority, which ended up falling flat (although the riding was ultimately one of the few in Quebec in which the Conservatives did better in 2008 than in 2006). Prior to 1993, the seat had flipped a couple times between the Liberals and the PC's (and featured the Rhino Party finishing in third ahead of the NDP in 1984). The Tories had hoped to lure Dumont into federal politics and take a run at this seat, but Dumont declined, and the 15% showing of the ADQ in the Riviere-du-Loup by-election that followed Dumont stepping down can't bode well for the Conservatives (in fairness, many Quebec Conservatives were supporting the Quebec Liberal Party candidate in the by-election). The BQ should hold onto the seat, and the real battle will be for second place. If the Liberals can muscle ahead of the Tories, that would show the party is taking root in francophone, rural Quebec, while a Tory hold of second place would allow them to ride the narrative of a Liberal falling in Quebec. I think ultimately the Liberals will finish slightly ahead of the Conservatives.
Probably the easiest seat to analyze, this is a safe BQ East Montreal riding. Real Menard never won less than 45% of the vote, and with the BQ lining up probable star candidate Daniel Paillé (although he must win a contested nomination first), this should be a fairly easy BQ hold. The Liberals won a respectable share of the vote last time around, and the NDP is hoping to maintain the relatively strong performance they had last time around, running 2008 candidate Jean-Claude Rocheleau. I've heard no word on potential Liberal or Conservative candidates.