With the first fiscal quarter of 2012 drawing to a close on Saturday, Massachusetts’s leading political campaigns have spent much of the past few weeks scrambling to raise last-minute funds and boost what will be their first financial reports since January.

The mandatory filing date, which accounts for funds raised and spent in the first three months of 2012, is not until April 15, but recent convention suggests some campaign’s could release these numbers as early as next week. Either way, the filing will be one of the most important insights yet into the state of each of the major campaigns for U.S. Senate and Massachusetts’s open Fourth Congressional District seat, analysts said.

“Money drives everything in campaigning. Period. End of sentence. While polls can vary, money is money,” said Democratic political consultant Mary Anne Marsh. “There’s no way to get around it because it is one of the few quantifiable measures you have of what kind of support you have and where it is.”

In anticipation of the deadline, a number of campaigns engaged with voters through contests that encouraged voter engagement. Various efforts asked for financial support and attempted to encourage grassroots participation.

In an email to Fourth District voters with the subject line “A Deadline Approaches,” Joseph P. Kennedy III asked his supporters to help provide the momentum now he would need to gather for the fall. He also launched a special “Raise the Roots” fundraising initiative among volunteers, singling out special “grassroots superstars” to feature on his campaign website.

Harvard Law School professor Elizabeth Warren’s campaign, which has focused on grassroots efforts since its inception, recently launched a NCAA tournament-themed political organizing challenge to engage supporters.

Fellow Democratic Senatorial candidate Marisa DeFranco has made similar appeals.

It is no surprise that much of the fervor has been limited to non-incumbents, Marsh said. For candidates like Sen. Scott Brown and Sean Bielat who have established donor networks, such efforts are less pressing.

“Often times when you are a new candidate, and you are just getting known, you have networks of money out of state that know you better than donors in your state,” Marsh said, citing the large out-of-state support Warren has received and Kennedy is likely to.

Such money is helpful, Marsh said, but often means little when it comes time to vote, and to make up for it, candidates will spend a lot of money setting up large grassroots networks that pay for themselves in votes.

“People who give you $25, $10, $100—those people are more likely to vote for you and work for you,” Marsh said.

Still, with the general election roughly six months away, the most important thing for Warren is that she fundraises more than her opponents, political analysts said. Warren has out-raised Brown each quarter since she entered the race last fall, but as of the end of 2011, she still trailed the incumbent by half—nearly $6 million.

“She’s done surprisingly well for a first time candidate, that said, no matter what she’s going to have to close the gap,” Marsh said.

The date will also bring the first financial reports from Kennedy, who entered the Fourth District race in January and is suspected to have a great deal of fiduciary backing from within the district and beyond, attributable largely to his family’s political prominence.

For Kennedy’s chief opponent, Bielat, who trails the Democrat by a wide margin in recent polls, the numbers could make or break his campaign, analysts said.

“As for Bielat, be on the lookout for large checks from national Republican players from out of State. If those dollars are not coming in, then those players do not consider his campaign a good investment,” former Boston City Councillor Lawrence S. DiCara ’71 said.

—Staff writer NIcholas P. Fandos can be reached at nicholasfandos@college.harvard.edu.