Stephen J. Kerrigan, the Democratic nominee for lieutenant governor three years ago, has jumped into the race for the 3rd congressional district, filing papers with federal regulators to form a campaign committee.

The longtime Democratic operative worked for the late US Senator Edward M. Kennedy and former state attorney general Thomas F. Reilly before holding senior roles for the national party, including CEO of the 2012 Democratic National Convention and president of the 2013 Presidential Inaugural Committee.

Kerrigan is also president of the Massachusetts Military Heroes Fund, a nonprofit that helps families of fallen servicemembers.

Sources familiar with Kerrigan’s plans said he planned to stop throughout the Third District, seeking to differentiate by adopting a retail approach. The Lancaster native, hailing from the district’s western swath, joins a crowded field hoping to succeed US Representative Niki Tsongas, who said in August she would not seek another term.


Kerrigan ran alongside Democratic gubernatorial nominee Martha Coakley in 2014, after emerging with a landslide victory in a three-way Democratic primary.

The Democratic field, while still taking shape, thus far includes hotel executive Abhijit “Beej” Das; former Boston City Hall chief of staff Daniel A. Koh; state Senator Barbara L’Italien; state Rep. Juana Matias; Cambridge city councilor Nadeem Mazen; and business consultant Loria Trahan.

On the Republican side, businessman Rick Green and former Navy pilot Scott Gunderson are running.

Jim O’Sullivan can be reached at jim.osullivan@globe.com. Follow him on Twitter at @JOSreports.