Rep. Jarrett Barrios (L), CARLO DEMARIA (C) and former Cambridge Mayor ANTHONY GALLUCCIO (R) engage in a heated debated at the ARCO Forum yesterday evening.

Mere days from the primary election, two of Cambridge’s biggest political stars went head-to-head last night in a rancorous yet inconclusive debate at the Kennedy School of Government’s ARCO Forum—a microcosm of a state Senate election that observers deem too close to call.

Former Cambridge Mayor Anthony D. Galluccio and State Rep. Jarrett T. Barrios ’90-’91 kept up a friendly tone with handshakes and smiles while acrimoniously jabbing one another on hot political issues such as affordable housing.

The two Cambridge candidates were joined last night by Carlo DeMaria Jr., an Everett alderman and owner of a Honeydew donuts franchise, a relative unknown and clear underdog in next Tuesday’s Democratic primary for the seat currently held by Senate President Thomas F. Birmingham ’72.

The winner of the Democratic primary will almost certainly win the seat in November, as no candidate from the Republican, Libertarian or Green Party filed for the seat.

Each candidate struggled last night to make a broad appeal to voters in what is a highly diverse Senate district that includes the tony Agassiz neighborhood of Cambridge and the blue-collar towns of Revere and Everett, as well as Harvard’s Yard dorms, the Law School, Adams House and the Quad.

The debate featured a series of questions from local journalists followed by an intense and personal round of candidate-to-candidate questions.

One journalist asked Galluccio how he would bridge the gap between Cambridge, which the journalist said has a reputation as full of “know-it-all liberals,”