In a small act of political theater meant to highlight his support for a pact that would limit outside spending in the Massachusetts Senate race, Democratic US Representative Edward J. Markey held an event Monday morning in which he sat next to an empty chair.

Markey called on his Senate opponent, Republican Gabriel E. Gomez, to join him and sign a so-called People’s Pledge. Under the pledge, candidates would make voluntary financial payments to charity every time an outside group spent money on campaign ads designed to benefit their campaigns.

Markey’s point was that without such a pact, groups that do not have to disclose their donors could back him and Gomez, which would obscure what people and groups were supporting each candidate. That, he said, would be bad for voters.

Advertisement - Continue Reading Below

“The people of Massachusetts have a right to know who is backing each of the two candidates, so they can make an informed judgment about the source of funding. That is key,” Markey said.

“I don’t want anyone to come in this state for either side,” he said. “I want this to be a battle between me and Gabriel Gomez.”

Gomez has repeatedly declined to sign a pledge.

“I will only take one pledge, and it’s the pledge I took when I was a naval officer, and that’s to protect and defend the Constitution of the United States,” he said last week. “Let’s be honest about it – politicians make pledges because nobody trusts them.”

During the event at the Omni Parker House in Boston, Markey declined to take a pledge on his own, saying the pact needed two people to agree to it in order to work.

Elizabeth Warren and Scott Brown signed a People’s Pledge in their contested 2012 Senate race. That agreement effectively kept most outside advertising out of the race.

A recent report by the nonpartisan group Common Cause Massachuetts determined that the Warren-Brown agreement reduced outside spending in the race and thus increased transparency and reduced negative advertising, when compared to other Senate races in 2012.

Markey’s campaign wasn’t the only group engaged in political theatrics Monday. The Massachusetts Republican Party greeted Markey with oversize checks as he left his event. A spokesman for the party said the checks represented the special interest money and money from political action committees that Markey has taken over his career.

The special election between Markey, a longtime US representative, and Gomez, a private equity investor and former Navy SEAL, is slated for June 25.