Democratic budget writers in both chambers face major tests this week with tough votes expected on spending and taxes in their fiscal 2008 budget blueprints.

Senate Democrats will have to stand together without defections if they are to adopt a budget resolution (S Con Res 21), as they can expect few, if any, GOP votes for the Democratic-written proposal. They likewise will have to unite to defeat GOP amendments that will attempt to cast the Democratic spending plan as heavy on taxes and light on spending discipline.

House Democrats, meanwhile, are still crafting their budget resolution. They have yet to decide how much to spend above President Bush’s proposed budget cap, and how much more they can assume in increased tax revenue without losing the support of moderate “Blue Dog” Democrats, who are developing an alternative budget plan.

The Senate budget plan, crafted by Kent Conrad, D-N.D., would reach a projected $132 billion surplus in fiscal 2012, compared with a $9 billion deficit in Bush’s proposed budget. Conrad’s plan, though, puts off to future years many tough decisions on taxes and spending, a nod to the difficult reality of winning adoption of a budget with a one-vote Senate margin.

Democrats will have to beat back likely attempts from Senate Republicans to enact new restrictions on spending and tax increases during up to 50 hours of debate this week, followed by a “vote-a-rama” on any remaining amendments.

“My impression is that Conrad and his staff are not breathing lightly just because they got this through committee,” said Robert Greenstein, executive director of the Center on Budget and Policy Priorities, a left-leaning group. Greenstein speculated that Conrad may have to accept some amendments he would prefer to oppose in order to advance the plan to conference, where the provisions could be stripped.

Conrad also will probably face attempts to weaken his proposed pay-as-you-go budget rules requiring offsets for new mandatory spending and tax cuts. Republicans are expected to offer amendments that would allow extensions of President Bush’s 2001 and 2003 tax cuts (PL 107-16, PL 108-27) without offsets. They could also seek to offer amendments reducing the growth of Medicare and Medicaid and cutting spending on domestic discretionary programs.

Conrad’s budget allows $18 billion more in domestic discretionary spending in fiscal 2008 than Bush requested. The president’s budget proposal sought a cut before inflation in those funds, which is not supported by the Democratic majority.

Meanwhile, House Budget Chairman John M. Spratt Jr., D-S.C., will unveil his fiscal 2008 budget plan this week, with a panel markup expected March 21 or 22, and floor consideration planned for the following week.

Although the Democrats hold a larger majority in the House than in the Senate, Spratt also faces the challenge of bridging the divide between liberal and conservative factions over spending and taxes.

Blue Dogs are drafting an alternative budget plan, said Rep. Jim Cooper, D-Tenn., a member of the Budget panel. Cooper would not provide details, saying that he had yet to see Spratt’s budget plan.

Greenstein said he expects the House budget plan to be similar to the Senate’s proposal, perhaps with slightly higher spending.

Rep. Artur Davis, D-Ala., another Budget panel member, predicted that the level of spending will fall short of what some liberal members want, while the level of revenue may be higher than the conservatives would prefer. But Davis said he expected that Spratt will be able to bring together the two sides.

It’s unclear by how much Spratt’s budget will exceed Bush’s spending level. He expressed surprise March 15 that Conrad had proposed a discretionary budget $18 billion higher than Bush’s, but said he hadn’t yet settled on a final figure.

Spratt also said last week that he would assume at least a one-year revision to the alternative minimum tax (AMT) to prevent it from hitting more than 20 million additional taxpayers. Conrad’s budget assumes a two-year revision, but requires any changes to be offset.

Spratt also plans to institute new pay-as-you-go rules and a plan to balance the budget by fiscal 2012. A House pay-as-you-go rule adopted earlier this year (H Res 6) is weaker in some respects than the Senate rule sought by Conrad, because it allows lawmakers to count future-year savings against earlier costs.

That could effectively allow Democrats to postpone painful offsets for AMT changes and new spending programs to future years. It’s unclear whether Spratt will include a tougher version of pay-as-you-go rules in his budget plan.