AUGUSTA – A deal between party leaders in the Senate to expand Republican representation on the powerful Appropriations Committee fell apart just a day before the new Legislature was sworn in.

Recognizing the near parity in the Senate, where Democrats hold a one-seat advantage over Republicans, 18-17, an agreement was brokered between party leaders to increase from three seats to four the number of senators with seats on Appropriations.

Newly installed Speaker of the House Glenn Cummings agreed to the change with the caveat that the proportion of House members to Senate members be kept the same as it is now. Overall, committee membership would have grown from 10 House members and three senators to 12 House members and four senators.

That’s when the deal fell apart.

“My caucus wasn’t ready to do that,” said Senate President Beth Edmonds, a Freeport Democrat. “The biggest concern was that by adding more people on the House side, it would diminish the power of the Senate majority.”

The Appropriations Committee is responsible for negotiating the details of the state budget. It’s the Legislature’s ultimate arbiter of state spending .

Lewiston state Sen. Peggy Rotundo was the chairwoman of Appropriations in the last session. She said Wednesday that increasing the size of the committee presented practical problems.

“That many members threatened to make the committee unwieldy,” Rotundo said. Also, more members would have come with a cost to pay for expanding the committee room to accommodate more members.

“We decided that there were other ways that, perhaps, could be more effective for us to work together,” Rotundo said. “There seems to be a real, genuine interest on both sides of the aisle in working together.”

“It was a disappointment,” said state Sen. Richard Rosen, the assistant Republican leader. “We thought we had an agreement to configure the structure of the Appropriations Committee in a way that reflects the close division in the Senate with an emphasis on really trying to reach a bipartisan budget agreement.”

Edmonds took responsibility for the breakdown.

“It’s my fault. I thought that my leaders and I had understood the will of the caucus,” Edmonds said. “I spoke too soon.”

State Sen. Peter Mills, a Skowhegan Republican who unsuccessfully sought the GOP gubernatorial nomination, has been an aggressive advocate for power-sharing in the Senate.

Earlier this month, he wrote a memo to the leadership of both parties outlining his ideas for broader Republican participation in the Senate’s structure, including increased seats on the Appropriations Committee.

“Democrats in the Senate didn’t want to give the House that much power,” Mills said. “They didn’t want to create any more trouble for themselves by enhancing the power of the House,” which he said is more liberal than the Senate.

“The differences between the Senate and the House could very well be bigger than the differences between the Rs and Ds in the Senate,” Mills said.

During opening day ceremonies, legislators in both parties concentrated on working together to strengthen the state.

While the Appropriations situation was a setback, it won’t likely set the tone for the session.

Democratic Senate leaders “agreed in good faith with us,” Rosen said. “But it’s always a step-by-step process in terms of building relationships. There is a willingness there to work together.”