WASHINGTON – Senate Republicans are employing a new tactic to force floor votes on some of their priorities – blocking floor debate on legislation most caucus members support.

Twice last week Republicans filibustered measures after Senate Democratic Leader Harry Reid, of Nevada, refused to offer opportunities for GOP amendments.

The filibuster deprived the measures the 60 votes needed to bring them up for debate. Republicans refused to okay consideration of bipartisan energy efficiency legislation sponsored by Sen. Rob Portman (R-Ohio) and Sen. Jeanne Shaheen (D-N.H.), expected to create almost 200,000 jobs. And they stood in the way of an $85 billion package that reauthorizes 50 tax breaks that expired at the end of 2013, including breaks for research and development, mortgage forgiveness and the deductibility of state and local sales taxes.

In both cases Republicans sought to offer amendments. The GOP wants to offer language to the Portman-Shaheen energy bill that would clear the way for construction of the Keystone XL pipeline intended to transport oil from Northern Canada to refineries in the U.S. And they want further consideration of their tax ideas, including repeal of a tax on medical devices instituted as part of the Affordable Care Act and the removal of a wind production tax credit from the bill. The measure had Republican support when it moved out of the Senate Finance Committee.

In each instance Reid, who controls the flow of legislation to the floor, moved to “fill the tree.” The Senate majority leader, Reid in this case, is recognized first when offering amendments on legislation. Majority leaders fill the tree by introducing amendments that block other senators from offering further amendments.

Depending on the legislation, one of four trees may be used. The first tree has room for three amendments, the second and third trees have room for five amendments and the fourth tree has room for 11. In filling the tree, the leader offers mostly placeholder amendments, leaving no slots available for anyone else’s amendment.

After filling the tree on the energy legislation, Reid offered to permit the GOP to offer the Keystone XL pipeline construction as a standalone bill but that was rejected – the measure likely would pass but would then face an insurmountable veto from President Obama.

Senate Republican Leader Mitch McConnell, of Kentucky, said his caucus took the unorthodox action of blocking bills it supports because Democrats have turned the Senate into a “graveyard of good ideas.”

“They’re completely allergic to anything constructive,” McConnell said. “They’re muzzling the people of this country — a gag order on the people we were sent here to represent — all to protect their power.”

McConnell called the situation “a scandal” and asserted that the public must be made aware of the situation because “this is bigger than any one bill.”

“It’s about protecting the right of the American people to have a say in what goes on in Washington,” McConnell said. “It’s about protecting the one institution that guarantees they’re heard. It’s about a party that’s become so afraid of losing its hold on power that they’re willing to do just about anything to hold onto it — even if it means rewriting the Bill of Rights, even if it means destroying this body, because that’s exactly what they’re doing.”

McConnell’s maneuver carries the support of other Republicans. Sen. Dan Coats (R-Ind.) noted that over the past 10 months Reid has allowed just nine roll call votes on Republican amendments.

“Hoosiers sent me to Washington to be their voice and right now that voice is being shut down,” Coats said.