Glenn Thibeault's announcement that he was leaving the federal NDP happened to coincide with his Sudbury riding association's Christmas party.

His surprising decision to leave the New Democrats and move to the Ontario Liberals prompted this response on Facebook from Sharon Murdock, president of the riding association: "I feel as if I have been slapped in the face. I can only imagine what my party is feeling. We work so hard to get our message out there and then, these kinds of things diminish what we believe," she wrote.

Murdock was hardly alone.

On Tuesday, the federal NDP's Ontario caucus convened a teleconference to try to understand what had happened to make Thibeault leave — and what to do next.

Glenn Thibeault

Glenn Thibeault's defection to the Ontario Liberals is a move no one seems to have seen coming, and left some in the party feeling 'slapped in the face.' (CBC)

A number of the MPs describe the overall reaction as "hurt." More than that, they say it hurt them in a way previous defections did not. Few understood how someone who had been caucus chair up until the beginning of December could have left the party so abruptly.

He certainly gave few clues.

In a conversation with leader Tom Mulcair on Sunday, Thibeault mentioned a "private offer," but gave no indication of another party, jurisdiction or defection. Sources say the conversation was about the direction the party needed to take in the New Year. There were no hints that Thibeault was considering leaving, at least right away.

And yet he did.

So, was it opportunism, and the possibility he will be catapulted to a cabinet position? He denies he was offered one.

Personality conflicts with the leader? That's something Thibeault also publicly denies.

No one really seems to know, and, frankly, many are too frustrated to offer reasonable explanations.   

There is, however, a consensus within the party that this was not a good day.

Stuck in the middle

There are now eight former NDP MPs who have either quit, moved on or been moved out since the party's electoral breakthrough in 2011 — to say nothing of those, such as deputy leader Libby Davies, who have decided not to run in 2015.

The NDP do like to remind people they managed to pick up former Bloc MP Maria Mourani, who will try to run for the NDP in Quebec in the next election. So, it's hardly a sinking a ship, but there does seem to be consternation.

In his latest analysis, CBC's polling expert, Éric Grenier, characterizes the NDP support as "stuck" at an average of 20 per cent of support nationally. Again, the NDP would point out this is the highest it has ever polled 10 months out from an election.

And yet, it can't seem to get much higher.

In spite of that, and minus this recent defection, the NDP has not had a bad run recently.

In the past months, it successfully rolled out a major policy plank in the form of a national daycare strategy; it confidently pushed back on the government's decision to start bombing in Iraq; and the leader continued to perform with aplomb in question period.

But when does all of that translate into a bit of momentum, a much-needed upward swing, some clear political points?

It's a problem the Official Opposition is clearly struggling to understand.

And it is running out of time to solve it.