There are two historical facts in Canadian politics. One is that Jews vote en masse for the Liberal Party. The other is that the Liberal party wavers between quiet and open anti-Israel hostility.
That Jews vote for the Liberals isn't much of a surprise. Just like in the States, most non-religious Jews (and frankly, too many religious ones) really believe that Judaism supports socially liberal policies like open access to abortion, gay marriage, unfettered immigration from the seediest parts of the world, etc. As a result, they vote according to what they think their Jewish consciences tell them to - Liberal.
On the other hand, the Liberal party in Canada has always been quite savvy about knowing where to direct its resources. Knowing that the Jews will vote for them no matter what, but that some immigrant communities like the Muslim ones might not, they generally concentrate their efforts on the possible votes, not the certain ones. If that means being anti-Israel, they'll do it. At the same time, the Conservatives have been identified as the anti-Jewish party and suffer for it at the polls each time. As I've said for years, the Liberals could run Hitler, y"sh, as their prime minister candidate and the Jews would still vote for them because they're worried that the Conservatives are the real anti-Semites.
Let's review the Liberal party's history, shall me? During World War II they worked to ensure no Jew would find refuge in Canada. Since that time their support of Israel has been, at best, luke warm. If they didn't advise the Canadian UN representative to vote against Israel, they generally advised abstaining. It was very rare for a Liberal government to openly support Israel wihtout some precondition. Appearing "balanced" was always the higher priority.
The Conservatives, on the other hand, have had the thankless task over the last couple of decades of actually being pro-Israel and suffering for it vote-wise amongst Muslim voters while gaining nothing from the Jewish community. Stephen Harper, the current prime minister, has gone further to support Israel than any other Western leader, especially the current occupant of the White House (that people don't want me calling Hussein anymore).
And so, in what seems to be the interminable leadup to the next federal election that doesn't look like it is going to happen for a while, the Conservatives have finally decided to point that out. And naturally the Liberals are all upset. After all, as the Liberal party they're the more Jewish, aren't they?
Perhaps Canadian Jews will finally sit up and take note of the track record