A New Jersey congressman has decided he wants to seek the U.S. Senate seat once held by fellow Democrat Frank Lautenberg.

Rush Holt on Thursday asked supporters to sign his petition to seek his party's nomination in the August primary. He's the first Democrat to formally announce.

The liberal was a scientist before he was first elected to the House in 1998, representing New Jersey's 12th District, which includes Mercer, Middlesex, Somerset and Union counties.

Conservative and former Bogota Mayor Steve Lonegan also plans to announce he'll seek the Republican nomination.

The special election will be held in October.

Gov. Chris Christie announced the election schedule on Tuesday, setting off a scramble for potential candidates who must file at least 1,000 signatures from supporters by 4 p.m. Monday.