METHUEN - With state Sen. Steven Baddour out of the race for Congress, other candidates, including state Rep. Barry Finegold of Andover, plan to fight hard for votes in Methuen and Haverhill.

"I do hope to work hard and earn the support of Baddour's constituency," Finegold, a Democrat, said yesterday.

Baddour's Senate district includes his hometown of Methuen and the city of Haverhill, two of the three largest cities in the congressional district. Congressman Martin Meehan will find out tomorrow if he is selected the next chancellor of the University of Massachusetts Lowell.

"The race is going to come down to Haverhill and Methuen," Baddour said of whoever runs. "It's a great position for us to be in. We're going to get to know the candidates really well."

Baddour made a formal announcement on the steps of Methuen City Hall yesterday that he was not running, saying he did not want to be a part-time father to his children, 5-year-old Isabella and 4-year-old Victoria.

Candidates like Eileen Donoghue, a Lowell city councilor, and Stephen Kerrigan of Lancaster, a 35-year-old former aide to U.S. Sen. Edward Kennedy and Attorney General Thomas Reilly, will be spending more time getting to know voters in Methuen and Haverhill.

"We don't know anyone in that end of the district who is planning to run," said Donoghue, who made her first campaign visit to Methuen last week at Mayor William Manzi's Irish luncheon. "I would plan on campaigning very heavily in that end of the district. Let's face it, we have a lot of things in common."

Baddour has estimated the cost of a congressional campaign to be $1 million. Finegold said yesterday he expects to spend at least that much because the cost of television advertisements alone could exceed $200,000 a week.

Finegold also said he will not give up his House seat to run for Congress.

"I'll be able to do both," he said.

Kerrigan announced yesterday he was forming a committee to explore a congressional campaign. He is a former Lancaster selectman who helped run the Democratic National Convention in 2004 and now works for a public affairs firm in Boston.

"This is a wide-open race, but it will unfold quickly," Kerrigan said in a statement. "As I await the congressman's decision, I need to have the pieces in place for what will be an important and dynamic campaign."

Other candidates include: state Rep. James Eldridge of Acton; David O'Brien, a member of the state and national Democratic committees, and Niki Tsongas, wife of former U.S. Senator and presidential candidate Paul Tsongas. Michael Sullivan, the Republican mayor of Lawrence, also is considering a run.

Baddour said he had been well-positioned for the campaign by having visited Washington, D.C., setting up a campaign team and getting $500,000 in donations committed.

The district covers 29 towns along the Interstate 495 corridor, from Berlin to Haverhill.

Officials in Methuen said Baddour had a strong chance of winning the seat, but support his decision to remain the local senator.

"I don't think he made the right decision, but he made it for the right reason," said City Councilor Joseph Leone. "We're in good hands if he's involved in Methuen."

Baddour said he is looking forward to continue to work in the state Senate on issues including transportation, the environment, and education.

"I am proud of my record of fighting for the needs of working families in the Merrimack Valley," Baddour said. "I am committed to continue showing my colleagues at the Statehouse that the Merrimack Valley is an incredible place to live, work and raise a family, and to fight for the investments we need to succeed."

Staff Writer Colin Steele contributed to this story.