AUGUSTA - Democrat Tom Allen said he's officially in the race for U.S. Senate as he dropped off nominating petitions with Maine election officials.

The six-term congressmen is challenging incumbent Republican Sen. Susan Collins. Allen dropped off petitions containing 3,000 signatures of voters from all 16 Maine counties at the Secretary of State's office Thursday.

Independents Laurie Dobson of Kennebunkport and Herbert Hoffman of Oqunquit also have announced their candidacies.

In a statement Friday, Allen says he supports tax cuts for the middle class and small businesses, universal health care, energy independence and a safe and responsible withdrawal from Iraq.