Bay State Democrats are working furiously to get the edge in the primary contest for the 5th district special election to replace departing Rep. Marty Meehan (D).

Two and a half months before the Sept. 4 primary, the field has narrowed to five candidates, which demonstrates how quickly things are moving.

There has been little turnover in Massachusetts’ Congressional delegation, so when word leaked that Meehan might vacate his seat to take a job in academia, wannabe Members pounced.

By the time the eight-term Member officially announced his departure from Congress, set for July 1, several candidates had campaigns ready to launch.

As of March 31, two candidates had raised more than $300,000 and one had more than $400,000 in their war chest.

With $311,000, state Rep. Barry Finegold actually raised the most primary money. Former Lowell Mayor Eileen Donoghue banked $413,000 but some of that was earmarked for the general election.

Republican Jim Ogonowski hopes to make the Oct. 16 general election race more than just a coronation of the winner of the Democratic primary.

The retired Air Force lieutenant colonel jumped into the fray April 24, saying he did so with eyes open.

“It’s a great opportunity for a Republican,” he told Roll Call last month.

The Lowell-based district is heavily Democratic — it gave Sen. John Kerry (D-Mass.) 57 percent of its presidential vote in 2004. Therefore, all eyes are on the Democratic primary.

Niki Tsongas, widow of the late-Sen. Paul Tsongas (D-Mass.), entered the race with the highest name identification.

She quickly won the backing of EMILY’s List, the Democratic fundraising powerhouse, and announced April 11 that Meehan’s wife, Ellen Murphy Meehan, would serve as her campaign chairwoman.

Since then Rep. Barney Frank (D-Mass.) has also endorsed her.

Tsongas had almost $310,000 cash on hand as of March 31.

Handicappers watching from Washington, D.C., might think Tsongas has things pretty well wrapped up, but all her competitors, and Democrats not affiliated with any campaign, caution against writing this primary off as a snoozer.

“I believe that to be completely untrue,” said Greg LaManna, state Rep. Jamie Eldridge’s spokesman. “I think the momentum is with us.

“Our biggest strength is the grass roots,” added LaManna, whose candidate had raised $106,000 as of March 31. “We’ve knocked on more than 8,000 doors already.”

Eldridge also won the endorsement of Democracy for America, the group started by Democratic National Committee Chairman Howard Dean and now led by his brother, Jim.

The group is making phone calls on Eldridge’s behalf and sends a strong signal that progressive Democrats are on his side, LaManna said.

Tsongas’ campaign is careful not to sound overly confident.

“Niki’s working hard. She knows, this being a special election, that she will have to earn every vote,” Tsongas spokeswoman Katie Elbert said.

“We think when people meet Niki and hear her positions on the issues, they think that she is the best person to represent them in Washington.”

Finegold was the first pol to express his interest in Meehan’s seat, should he vacate it.

“It’s been a great couple of months. It started out with a bang in that Barry raised the most primary money in the first filing period,” said Nairi Tashjian, Finegold’s spokeswoman.

“When Barry gets out on the streets and greets voters door to door, he resonates,” Tashjian said. “He was born and bred in [this] area and he just really connects with voters.”

Tashjian said Finegold has put together a team of nationally respected consultants including Dane Strother of the well-known media firm Strother-Duffy-Strother.

Most candidates say the biggest hurdle is the condensed time frame in which they must work.

“It’s a short campaign and that’s the real challenge,” Tashjian said.

Finegold has an “aggressive” canvassing operation, according to one Democratic operative familiar with Massachusetts who did not want to be named.

Tsongas and Eldridge are also out in force on the ground.

Most observers agree Tsongas, Finegold and Eldridge are the most formidable contenders right now.

Donoghue and state Rep. Jim Miceli, who had banked just $10,600 as of March 31, are by no means out of the race, the Democratic operative stressed.

The operative said placing bets on the outcome of the primary now would be foolish.

“You never know what’s going to happen with a special election, not to mention the fact that it’s the day after Labor Day — you just don’t know who will turn out,” the source said.