HARRISBURG — Fundraising by the candidates for Pennsylvania governor approached the $40 million mark as they began pouring millions into expensive TV advertising to get out their message, according to campaign finance reports filed Tuesday, six weeks out from the primary election.

The four Democrats and two Republicans raised $5.3 million between Jan. 1 and March 31, on top of the roughly $34 million they collected last year.

Democratic front-runner Tom Wolf revealed he spent by far the most, including nearly $4.5 million on the TV ads he launched in late January that are widely credited for his surge in early polling. That accounted for most of his $5.4 million in expenditures over the three-month period, which also included $143,000 for online ads and services, $113,000 for polling and $26,000 for fundraising.

Wolf, who donated $10 million — some of it borrowed from a bank — to his campaign, raised $611,000 during the last reporting period, bringing his campaign total to about $14 million. He reported having $7.1 million in cash — more than any other candidate — as of March 31.

Wolf’s biggest contributions included $200,000 from fellow York businessman Louis Appell and $50,000 from George Hodges, chairman of York Water.

On the Republican side, Gov. Tom Corbett, who faces token opposition in the GOP primary, took in $1.4 million, pushing his total to nearly $9 million. After nearly $3 million in expenditures in the last three months, he had almost $6 million on hand.

Corbett’s biggest contributors included John S. Middleton, a Philadelphia Phillies co-owner and major GOP donor, who gave $250,000. Contributions from the highway construction industry zoomed past the $160,000 mark and the political committee and chief executive of Ohio-based coal mine operator Murray Energy gave Corbett’s campaign at least $50,000.

Corbett’s only foe in the GOP primary, Ardmore conservative activist Bob Guzzardi, reported raising $4,500 and spending $4,100.

Democratic U.S. Rep. Allyson Schwartz raised more money than any other candidate between January and March — $1.6 million — bringing her campaign total to about $8 million.

Schwartz’s biggest contributor was Emily’s List, a national group that works to elect women who support abortion rights, which gave her $355,000. She also received $50,000 from the Local 98 of the International Brotherhood of Electrical Workers in Philadelphia.