AUGUSTA – Democratic U.S. Rep. Tom Allen has filed petitions with state election officials to appear on the November ballot as a candidate for U.S. Senate in what is shaping up as a five-person field.

The six-term congressman, who represents southern Maine’s 1st District, said nominating petitions containing 3,000 voter signatures were dropped off Thursday at the Secretary of State’s Office. Allen is challenging incumbent two-term Republican Sen. Susan Collins.

Independents Laurie Dobson of Kennebunkport and Herbert Hoffman of Ogunquit also have announced their candidacies. Thomas Ledue of Sanford wants to challenge Allen for the Democratic nomination for Senate.

Allen said in a statement Friday that he supports tax cuts for the middle class and small businesses, universal health care, energy independence and a safe and responsible withdrawal from Iraq. Collins has touted her experience in the Senate on homeland security and defense issues.

The Senate contest is on track to set a record for campaign spending in Maine. By the end of 2007, Allen and Collins had raised a combined total of about $7.5 million. Collins had raised nearly $4.6 million and Allen about $3 million.

Several other candidates have beaten the March 17 deadline for turning in petitions to get their names on the June primary ballot.

In the 1st District, Democrats Michael Brennan and Ethan Strimling of Portland and Stephen Meister of Winthrop have filed, and Republican Charles Summers of Scarborough has dropped off petitions.

Others who have announced candidacies include Adam Cote of Portland, Mark Lawrence of Kittery and Chellie Pingree of North Haven. On the Republican side, Dean Scontras of Eliot hopes to challenge Summers.

In the 2nd District, incumbent Rep. Mike Michaud has submitted nominating petitions. Republican John Frary of Farmington wants to challenge Michaud.