Senate Democrats were eerily subdued Monday as details of an emerging deal leaked from White House and Republican officials, but the quiet masked the disgruntlement, not just from liberals but also more moderate members up for re-election in 2014.

Senate Majority Leader Harry Reid, D-Nev. — who in the year’s closing hours left much of the negotiating to Minority Leader Mitch McConnell, R-Ky., and Vice President Joseph R. Biden Jr. — waited almost the entire day before calling members together to review the details of their proposal. And when he did, he invited Biden to sell it to his restless membership. Reid also has not indicated whether he could support the plan, which began to take shape early in the morning.

Given that Democrats were widely considered to have been in the position of leverage, several members and aides privately grumbled that the White House had ceded too much ground in not sticking to its promises to allow taxes to rise on those making more than $250,000. Adding to the displeasure was the president’s failure to secure perhaps the biggest chit Democrats wanted: a way forward on the debt ceiling.

“As I see this thing developing — quite frankly, as I’ve said before — no deal is better than a bad deal, and this looks like a very bad deal, the way this is shaking up,” Sen. Tom Harkin, D-Iowa, said on the floor Monday. “If you’re making more than $250,000, you’re not middle class. You’re the top 2 percent of income earners in America.”

“This is one point in time where decisions that are made on this so-called deal, decisions that are made could lock in for the next 10 years what kind of a country we’re going to be, what kind of a society we’re going to be,” Harkin continued. “So we better be darned careful.”

In July, all but two members who caucus with Senate Democrats voted for a symbolic measure that would let expire tax breaks for those with incomes more than $250,000. The two members who opposed it are both retiring. Yet White House officials seemed to indicate Monday that Senate Democrats had weakened their hand in the tax debate.

Regardless, any deal struck — if any is struck at all — will likely set up a series of difficult votes for members who face re-election in 2014. Throughout the 112th Congress, Reid tried to shield his in-cycle members from tough votes. With so much still up in the air — from an extension of the debt limit to how to deal with the sequester to entitlement cuts and tax code reform — senators will likely be asked to repeatedly vote on tricky budget issues in 2013.

“It’s disappointing we couldn’t get it all now, but as the president said today, we’re going to have to do it in phases,” said Sen. Mary L. Landrieu, D-La., who is up for re-election in 2014.

Landrieu noted that the “problem” with the deal as configured is that it likely will not reduce the deficit. The White House would be able to secure about $600 billion in revenue from raising tax rates on incomes over $400,000 for individuals and $450,000 for families, but it would lose just as much through permanent extensions of other measures, such as reducing the reach of the alternative minimum tax. The Tax Policy Center at the Brookings Institution calculated the AMT fix would cost $2.7 trillion from 2011 to 2022.

“The Republicans have refused to allow taxes to be raised on those on the highest levels, they’ve had to concede that point, and middle-class families have been protected, but the deficit is still a problem that needs to be addressed,” Landrieu said.

“The money is not being spent; it’s being given back to middle-class families in the form of tax relief,” the Louisiana Democrat said.

Many aides to other in-cycle Democrats approached for this story did not want to comment publicly on a deal not yet done. But it’s clear the White House and Senate leaders, who seemed resigned to a package of this scope, have some selling to do.

“The White House needs to do a sales pitch,” one Senate source said.