BOSTON - U.S. Sen. John Kerry may have competition for the Democratic Senate nomination in 2008.

Gloucester defense attorney Edward O'Reilly said yesterday he will formally announce his bid at this weekend's Democratic Party convention in Amherst.

He'll also need to collect 10,000 signatures by May 6, 2008, to gain a spot on the Democratic primary ballot.

The former Gloucester city councilor and School Committee chairman said Kerry's vote to authorize force in Iraq in 2002 is one reason why he's running. O'Reilly, 53, said he would vote to immediately withdraw troops from Iraq.

"Immediately, like today," O'Reilly said. "And keep a temporary force in the area to fight al-Qaida."

He also said Kerry mishandled contributions to his presidential campaign - including $2,000 O'Reilly donated. O'Reilly said Kerry should have used money in his account to challenge the results in Ohio, the state whose electoral college votes put George W. Bush ahead. There were allegations of voter fraud in Ohio.

Instead, O'Reilly said, Kerry is using the money left from his presidential bid to help fund his re-election campaign.

"There are a lot of things that have been building up," O'Reilly said of his issues with Massachusetts' junior senator.

Kerry was elected to the Senate in 1984. His closest race came in 1996, when then Gov. William Weld, a Republican, challenged him in the general election.

As O'Reilly announces his run, Kerry is kicking off his re-election campaign. Kerry is holding events across the North Shore on Monday and later that evening is holding a fundraiser in Boston expected to net $250,000.

Amy Brundage, a Kerry spokeswoman, said the senator looks forward to the campaign. She said Kerry is "leading the fight in the Senate to end the war in Iraq (and) bring the troops home."

This is no quixotic venture - it's one that has been in the making for years, O'Reilly said.

O'Reilly said he'll leave his law practice in the hands of a partner while he campaigns full-time.

He said he's not concerned about raising money. A supporter of Howard Dean's presidential campaign, O'Reilly said he hopes to follow Dean and raise small contributions from many donors.

Gloucester Democratic Committee Treasurer Patrick Abegg said he wasn't surprised by O'Reilly's announcement.

"He has always been passionate about it," he said.

Abegg said odds may be stacked against O'Reilly but sees competition as a good thing.

"It's always a challenge taking on an incumbent," he said. "Even if you don't succeed, it's good to bring light to some of the issues that are important to you."

O'Reilly has been an attorney for 25 years. He also is a former firefighter, corrections officer at Norfolk State Prison and Gloucester lobsterman. He hails from Watertown, and has degrees from the University of Massachusetts and New England School of Law.

Asked whether he can beat Kerry, O'Reilly said that's the wrong question. It's whether voters want change.

"It's not whether I can beat him," O'Reilly said. "If they want a new senator, it's up to them."

Staff reporter Julio Chuy contributed to this story.