They join state Rep. Carl Sciortino in expressing interest in the seat.
The growing list of potential contenders for the seat reflects the prevailing opinion in Massachusetts that Markey has a relatively easy path to the nomination, and ultimately, election to the seat vacated by Secretary of State John Kerry.
Since former Sen. Scott Brown (R-Mass.) announced he would not run for the seat, Republicans have been unable to recruit a strong candidate, and few Democrats or Republicans in the state expect the eventual Republican nominee to come out on top.
And though Markey faces a primary challenge from Rep. Stephen Lynch, he has a large financial advantage on Lynch and the backing of a number of big Democratic names in Massachusetts and Washington.
However, a recent poll showed Lynch slightly closing Markey's substantial lead. Markey still holds a double-digit lead on Lynch, but that lead diminished from 33 percentage points in January to 15 points in February.
No potential contenders have yet announced interest in Lynch's seat.