PORTLAND – Former Maine state Sen. Chellie Pingree has filed with the Federal Elections Commission to launch a campaign for Maine’s 1st District congressional seat, which is now occupied by fellow Democrat Tom Allen.

Allen, of Portland, has signaled he’s ready to run against Republican U.S. Sen. Susan Collins next year, but has made no announcement so far.

A number of Maine Democrats have been eyeing Allen’s congressional seat amid speculation the six-term congressman will run for the Senate. In addition to Pingree, they include York County District Attorney Mark Lawrence, former state Sen. Michael Brennan of Portland, and Portland lawyer Adam Cote, a former soldier in Iraq.

Pingree, of North Haven, ran against Collins in 2002 but lost. She later served as president of Common Cause but announced earlier this year she was stepping down to consider political opportunities in Maine.

An aide to Allen told WGME-TV that the congressman has no timetable for making an announcement on his political plans.