The Senate's #2 Democrat Dick Durbin voiced the worry that presidential ambitions and strong opposition from the Tea Party might yet derail the budget deal approved by the House last week.

The Hill:

Durbin estimated that Democrats will lose three members of their caucus on the vote, which means they'll need at least eight Republicans to cross the aisle and vote with them.

The challenge Democratic leaders face in trying to round up the vote has been compounded by the outspoken opposition to the deal from Republicans weighing presidential bids and a slew of Republican primary races in 2014.

"A handful of members of the Senate are vying for the presidency in years to come and are thinking about this vote in that context and others are, frankly, afraid of this new force, the Tea Party force, the Heritage Foundation force, that is threatening seven out of the 12 senators running for reelection," Durbin said on CBS's "Face the Nation."

Sens. Ted Cruz (R-Texas), Rand Paul (R-Ky.) and Marco Rubio (R-Fla.), who are weighing presidential bids in 2016, have all blasted the deal.

No Senate Democrat has yet publicly voiced their opposition to the deal negotiated by Senate Budget Committee Chairwoman Patty Murray (D-Wash.) and her counterpart, Rep. Paul Ryan (R-Wis.), but Durbin expects three defections.

"We will need about eight Republicans to come our way. I feel we'll have a good strong showing from the Democratic side," he said.

Senate Republican Leader Mitch McConnell (Ky.) and Senate GOP Whip John Cornyn (Texas), who both face Republican primary challengers, have signaled they will vote against the bill.

Other Republicans who face Tea Party challengers include Sens. Thad Cochran (Miss.), Pat Roberts (Kan.), Lamar Alexander (Tenn.).

The Club for Growth, a group that has spent millions of dollars in past Republican primaries, opposes the deal and has pledged to score it on its annual legislative scorecard.

A vote for the budget agreement could spur the group to get involved in one of next year's races.

Durbin said he hoped Senate Republicans would be persuaded by Speaker John Boehner's (R-Ohio) pushback against conservative groups last week.

A majority of Republicans not running next year will probably be key for Democrats who need at least 4 more Republicans to win a cloture vote. On board already are Senators McCain, Collins, Flake, and Burr. There may be other Republicans who will oppose the budget deal but would vote for cloture.

Durbin is close but it's not in the bag yet. The longer the debate goes on, the more intense the opposition becomes. A cloture vote was orginally scheduled for tomorrow, but that deadline is up in the air. With the Christmas recess looming, a vote by the end of the week would be necessary if the deal is going to be passed this year.