British Columbia's spring election campaign has taken on a dark tone before it even begins, as the opposition New Democrats rolled out their campaign bus a week early on Tuesday, with fresh attacks against the Premier.

The NDP's attempts to paint Premier Christy Clark as a politician beholden to her "rich donors" follows the governing Liberal Party's own ads dismissing the New Democrat Leader John Horgan as weak and indecisive. Such attacks provide an early hint at the potentially dark tenor of the campaign between now and the May 9 vote.

The New Democrats, who have internally blamed a failure to go negative in 2013 for their defeat in that year's election, have already released pre-election attack ads targeting Ms. Clark's fundraising practices. Liberal fundraising has come under scrutiny for the volume and size of contributions from large corporate donors – and the government's refusal to impose limits.

Story continues below advertisement

Read more: Despite debacles, parties and pollsters will still be surveying voters – cautiously

Mr. Horgan continued that line of attack at a campaign launch event on Tuesday, declaring: "The wealthy have had their premier. It's time we had a premier that was working for you."

The NDP is still recovering from its ill-fated campaign in 2013, when it went into election day expecting an easy victory but instead watched the Liberals win a fourth-straight majority. That campaign has been thoroughly studied by the New Democrats and it is, in many respects, defining the party's approach this year.

An internal party review following the 2013 defeat concluded the party failed to "prosecute" the Liberal record, among other missteps. The party has sworn off the positive approach offered by then-leader Adrian Dix.

Glen Sanford, the B.C. NDP's deputy director, said in an interview that the the party will spend the campaign weaving a narrative that contrasts Mr. Horgan with the Premier: "Christy Clark is working for her rich donors. John Horgan and the NDP will work for you."

Mr. Sanford rejected the suggestion that "rich donors" is overheated because he said the sentiment is consistent with what the NDP has been hearing from voters. "If anything, we're expressing their sentiments rather kindly," he said.

On Sunday, the NDP launched three new TV ads attacking the Liberal record on housing and increasing costs for services, and noting that the RCMP has launched an investigation, at Elections BC's request, into political contributions in B.C. That investigation followed a Globe and Mail report that found lobbyists making indirect contributions and then getting reimbursed by their clients, which is illegal.

Story continues below advertisement

The NDP ads featured the tagline: "Christy Clark. Not Working for You."

The Liberals have also been running ads against Mr. Horgan, reviving an old symbol of the leader as a weather vane changing direction with the wind. The ads warn: "Same weak leadership. Same old NDP."

Asked about the early start, Mr. Horgan said in an interview that the B.C. Liberals have been spending public money to campaign, a reference to government advertising that some have said benefits the incumbents. Provincial government data show ad spending has spiked in pre-election years in the past three campaigns, including this year's, which the auditor-general flagged as a potential issue. The province's communications department has also ramped up its activities, sending out 557 media releases in March, compared with an average of between 150 and 250 in typical months.

"I am out spending money that was raised by the NDP to talk to people about the issues that matter to them," Mr. Horgan said.

On the question of what the NDP would do differently this year compared with the last campaign, Mr. Horgan said: "The difference is that we're going to win by going out and talking to people about the issues that matter to them."

With the election date fixed, B.C.'s main parties have been effectively campaigning for months. However, the NDP has made things more official with campaign stops planned in Metro Vancouver, the Okanagan and the Interior through Friday. On Sunday, Mr. Horgan will be addressing a major rally in Surrey – a key election battleground.

Story continues below advertisement

The review following the NDP's 2013 loss produced a 42-page document that concluded the NDP lost because "the Liberals prosecuted us better than we prosecuted them;" the NDP allowed the Liberals to raise "grave doubts" among voters about Mr. Dix without countering them "despite ample opportunity to do so;" and that failing to take on Ms. Clark "absolved" the Liberals from accountability. In that last campaign, Mr. Dix avoided sustained criticism of the Liberals, preferring a commitment to positive campaigning to, he said, address voter cynicism about politics.

The B.C. Greens have a major event this Thursday with Leader Andrew Weaver that the party is billing as a "surprise unveiling." The party will have a campaign bus for the first time this year; it will be a biodiesel vehicle.

There was no comment Tuesday from the BC Liberals on their campaign plans, but in a statement, the party said it hoped Mr. Horgan would use the extra campaigning time to clarify his job-creation plans.

The current standings in the legislature are 47 Liberal, 35 New Democrats, one Green and two Independents. The May 9 election includes an extra two ridings that were not in place in 2013, bringing the total number of seats to 87.