In the war on terror, the political battle lines are now clearly drawn.

NDP Leader Tom Mulcair announced Wednesday that his party will oppose Bill C-51, the Conservative's anti-terrorism law. In doing so, Mulcair puts his party clearly at odds with the government and the third-party Liberals.

"Stephen Harper's new law is sweeping, dangerous, vague and ineffective," Mulcair told reporters before kicking off debate on the bill in the Commons.

"It doesn't do things that are proven to work and puts politics ahead of protecting Canadians. Even when he introduced the legislation, Harper chose a campaign-style event. and made remarks that most regrettably targeted Muslim communities."

With that, Mulcair neatly summarized what’s ahead.

First, the merits of the bill will be reviewed, if on a truncated schedule. The Conservatives moved Wednesday to limit debate at this stage in the bill's review. Additional motions to cut off debate and study are all but guaranteed as the Conservatives rush to get the bill passed before Parliament rises for the last time ahead of the 2015 election.

Second, public safety is shaping up as one of the key issues in the coming campaign. Sides have to be taken, choices offered.

Mulcair did what leaders off the Official Opposition do, in announcing the NDP will oppose the bill each and every step along the way.

The Conservatives insist their proposals are both common sense and absolutely necessary.

Bill C-51 overrides privacy and other legislative limits to sharing information relevant to terrorism investigations. The proposed legislation gives the Canadian Security Intelligence Services (CSIS) the power to disrupt potential terrorist plots, and police broader powers to detain suspects who "may" carry out rather than the higher standard of "will carry" out a terrorist activity

Prime Minister Stephen Harper blasted the NDP's criticism of Bill C-51, saying its views are 'more and more irrelevant.' Conservatives are pushing to get the anti-terrorism bill passed before Parliament rises. (Sean Kilpatrick/Canadian Press)

"As the NDP's positions on this issue become more and more irrelevant, more and more unconnected to Canadians' real concerns, their statements on this issue become more and more extreme," Harper told the Commons.

The Liberals, consistent with their place in Canada’s political order, are straddling the centre, positioning themselves between the oppose-at-all-costs NDP and the ram-it-through at any cost Conservatives.

Liberal Leader Justin Trudeau says his MPs will support the bill, but plans to introduce two dozen or so amendments aimed at soothing public concerns that the bill gives CSIS too much power to snoop, and police too much latitude to violate Canadians' rights. If the government accepts none of them, well, the Liberals will campaign on them this fall, Trudeau says.

The amendments include a mandatory review of the entire law after three years, and proper parliamentary oversight of CSIS and the police.

Like Mulcair, Trudeau reached out to Canadian Muslims, assuring them that the October attacks on two Canadian soldiers in broad daylight were not viewed as consistent with their values.

And just to show he’s also capable of a bit of political posturing, Trudeau got in a partisan shot of his own aimed at Mulcair.

"The fact is the NDP has not once in its history supported strengthening anti-terror measures in this country."

But what about the bill itself?

Liberal Leader Justin Trudeau has said his party will support the bill, though it plans to offer amendments. If those amendments aren't accepted, Trudeau says the Conservatives can expect them to become a campaign issue. (Sean Kilpatrick/Canadian Press)

‎At the core of the NDP's concerns: the legislation sets out a long list of activities that could trigger intervention by security agencies: from blocking pipeline construction to threatening the economic stability of the Canadian economy.

Mulcair said it's a gross overstep, but consistent with the Conservatives’ strategy of using perceived threats as a political bludgeon.

The prime minister said it’s Mulcair who is pandering for votes, because the bill includes explicit guarantees that terrorism activity does not include "lawful advocacy, protest dissent and artistic expression." How that will be interpreted isn't clear, and lawyers everywhere are no doubt plotting the first charter challenge once the bill becomes law.

The other central arguments against the bill are that there's no meaningful political oversight of CSIS or police actions, and as Mulcair set out Wednesday, no evidence new powers are even needed.

He ran through the examples: the arrest of the Toronto 18; the foiling of a plot to blow up a VIA train; and just last week, the arrest of young people who allegedly planned to open fire on shoppers at a Halifax mall. All accomplished under existing laws.

For that Harper had no answer.

Lessons from 2001

Trudeau notes the Liberals had to act quickly in 2001 in response to the Sept. 11 attacks, bringing in what at the time appeared to be draconian measures to deal with the new reality that planes could be used as weapons of mass destruction in North America.

There are lessons to be learned in the exhaustive review done in 2001, when the Liberals introduced sweeping anti-terrorism measures.

First: there were full public hearings by both the Commons and Senate into the bill. The two houses did their work at the same time, often interviewing the same witnesses. It expedited the process, without rushing through the law. Canadians heard arguments both for and against.

Second, it led to some meaningful amendments, including a five-year limit on the most controversial powers: investigative hearings and preventive arrest.

In the end, those powers were never used, even as police and security agencies confronted increasingly sophisticated, increasingly local threats to public safety.

But 2001 wasn’t an election year — 2015 is. And as MPs begin their review of C-51 they’ll have one eye on the bill before them, and the other on what it could mean in the campaign that beckons in the months ahead.