Connecticut Sen. Joe Lieberman said voting for the tax deal is a political winner for Democrats.

"Everybody's going to make their own political judgments, but to me there's so much good in here for working families — middle-class families — that voting for this package is very easy to defend," he told reporters at the Capitol on Tuesday.

Lieberman, an independent who caucuses with Democrats, is up for reelection in 2012. He said Democrats didn't have the votes to sunset the tax cuts for wealthy Americans.

"What’s the alternative? To have gridlock, which means that everybody's taxes go up on Jan. 1, including middle-class, lower-income people?" he said. "In a bipartisan agreement, you never get everything you want."

Lieberman noted that as part of the deal that extends the Bush-era tax rates for all income brackets, Democrats got a 13-month extension of unemployment benefits, a payroll tax cut and extensions of the childcare tax credit and the college tuition tax credit.

"I think the benefits are very strong in this package," he said. "I think the alternative was for the economy to go deeper into recession."

More than half the Senate Democrats will vote for the deal, Lieberman predicted.

Senate Democrats heard about the deal from Vice President Joe Biden during their weekly lunch at the Capitol on Tuesday.

"There was emotion" during the meeting, said Lieberman.

"There were a couple who were asking, shall I say, vigorous questions about it, but I thought the vice president handled it well," he said. 

Lieberman also praised President Obama's handling of the negotiations, telling MSNBC on Tuesday the president "negotiated a good agreement."

—This post was updated at 3:36 p.m.