(CNN) - The political fistfight in Massachusetts to fill the last three years of the late Sen. Ted Kennedy's seat is also turning into a big bucks battle.
With five days left until Bay State residents vote in Tuesday's special election, both sides are publicizing the campaign cash they've raised in the past few days.
A Wednesday on-line fundraising pitch by the late senator's widow, Vicki Kennedy, for the Democratic candidate, Massachusetts Attorney General Martha Coakley, has brought in more than $600,000 as of early Thursday, according to a source close to the campaign.
The campaign of Republican candidate Scott Brown, a state senator, announced Tuesday that a fundraising pitch raised $1.3 million over a 24-hour period.
Coakley has spent $605,000 to air campaign television ads since Friday, according to Evan Tracey, president of Campaign Media Analysis Group and CNN's consultant on political advertising. Brown has spent $550,000 since Christmas. And those figures don't include the massive amount of ad dollars shelled out by national and state political party organizations and independent groups in the past few weeks.
Why the surge in fundraising and spending? Because the Democratic Party's supermajority in the Senate's at stake.
If Brown pulls an upset and defeats Coakley, the Democrats will lose their 60 seat filibuster-proof coalition in the chamber, which could severely threaten their chances of passing a health care reform bill to hand to President Barack Obama for his signature.
Brown is hoping to become the first Massachusetts Republican to win a U.S. Senate seat since 1972. Independent Joseph Kennedy, a third party candidate who is not related to the late senator, is also in the race.
The 77-year-old Kennedy died of brain cancer in August. Democrat Paul Kirk, a long time adviser and friend to Kennedy, is serving as his interim replacement.
Follow Paul Steinhauser on Twitter: @psteinhausercnn