WASHINGTON — For the second time, Senate Democrats on Tuesday blocked a vote to move forward on a resolution rejecting the Iran nuclear deal, protecting President Obama’s key foreign policy initiative.

The measure failed Tuesday to gain the 60 votes needed to advance – just as it did last Thursday. The vote was 56 to 42.

Maine’s senators split their votes. Republican Sen. Susan Collins voted in favor of moving forward while Independent Sen. Angus King was opposed to moving forward.

Though the measure is unlikely to advance, Republicans staged the Senate vote to make political points against Democrats and in future Senate races. They point to polls showing Americans have reservations about the deal.

The second vote was not the final word in the Senate. Frustrated with the outcome, Majority Leader Mitch McConnell, R-Ky., set up a vote Thursday on a measure that would bar Obama from lifting sanctions on Iran unless Tehran recognized Israel as a state and released U.S. prisoners held in Iran.

“Either way this debate will continue,” the Republican leader said.

Despite McConnell’s maneuver on a politically fraught measure certain to show up in campaign ads and fundraising appeals, Democrats were expected to again hold together and block the bill.

As debate resumed Tuesday, McConnell accused Democratic senators of refusing to let the Senate vote on the deal.

“A strong, bipartisan majority of the House of Representatives voted to reject the deal. A strong, bipartisan majority of the Senate would vote to reject the deal too,” McConnell said. “If only Democrat senators would stop blocking the American people from even having a final vote on one of the most consequential foreign policy issues of our age.”

Other Republicans who spoke out against the deal said even Democrats have publicly noted the drawbacks to the deal. Sen. John Cornyn, R-Texas, displayed black-and-white placards printed with quotes from pro-deal Democrats who have expressed reservations about the agreement.

However, Sen. Dick Durbin of Illinois, the No. 2 Senate Democrat, said Tuesday’s vote – and the possibility of another one later in the week – was an exercise in futility.

“We had this vote last week,” Durbin said. “I don’t know why we’re doing a replay of this.”