Senate Democrats might be facing the greatest challenge of their brief majority as they battle on two fronts to pass legislation this year — taking on an all-but-certain Republican filibuster and tackling a fresh and prolific round of veto threats from President Bush.

In recent weeks, Bush has aggressively waged a campaign to veto pieces of the Democratic platform, including a recently drawn bipartisan farm bill, a housing stimulus package, the Federal Aviation Administration reauthorization measure and a must-pass $200 billion-plus Iraq spending plan. The president has flexed his veto power before, rejecting eight of the Democrats’ bills last year and one so far this year, but the ante has been upped as the Senate sprints to wrap up its work by Memorial Day.

The reality of Bush’s veto threats along with regular GOP filibusters is leaving Democrats with few options to rack up voter-friendly accomplishments in a pivotal election year. Senate Democrats must either make concessions to Republicans, try to line up support for veto overrides, or embrace patience and bank on picking up as many as nine Senate seats in November and winning back the White House after eight years.

Sen. Ben Nelson (D-Neb.) said the landscape provides Democrats with little room to get things done with just a few months to go in the 110th Congress: “It’s the way it’s going to be until the end. We’re adjusting to that because it’s necessary.”

Nelson’s assessment isn’t unique among Senate Democrats, who almost universally say they aren’t counting on much legislation outside of must-pass bills getting through before January — and predict that Democrats won’t pay for it with voters.

“There’s no question in my mind that the risks are greater for” Republicans, said Sen. Bob Menendez (D-N.J.). “The nation knows the executive branch is controlled by a Republican president who put us where we are today.”

“If that’s the legacy he wants to leave in his last eight months, so be it,” Menendez added. “But he’s not going to intimidate Congressional Democrats who want to make change or try to make change.”

Democrats have made Republican “obstructionism” a cornerstone of their message this year, charging that GOP lawmakers and the president have prevented them from ushering in the changes they promised when they assumed control of the House and Senate in 2007. They argue that barring a new willingness by Republicans to compromise in the coming months, they will need voters to deliver more seats in the next Congress and control of 1600 Pennsylvania Ave.

Senate Democratic Conference Secretary Patty Murray (Wash.) said the GOP road map for 2008 has become clear: “It certainly seems to me they are using every tool out of their toolbox” to stop Democrats from legislating. “This country is really suffering. Stopping things and saying ‘no’ doesn’t accomplish anything.”

But Senate Republicans are betting that there will be a payoff if they line up behind Bush’s veto pen and stick to a strategy of preventing Democrats from getting the 60 votes needed to overcome a filibuster and pass legislation. They also hope they can effectively accuse Democrats of pushing a platform of runaway spending, which would not win points with an economically strapped electorate.

Asked whether the benefits of vetoes and filibusters outweigh the possible risks for Republicans this year, one senior Senate aide said: “Hell yeah. If they are going to argue that they wanted to raise taxes and Republicans stood in the way, I know how that will play, and we’ll cut the ad for them.”

For his part, President Bush argues his veto isn’t linked to election-year politics but rather to head off policies that “negatively impact our national security and our economy,” said White House spokeswoman Emily Lawrimore. She pointed to the farm bill as an example, saying the president thinks it would “drastically expand the size and scope of government and doesn’t include the meaningful farm program reform the president has called for.”

Unlike most Bush veto threats that have solid Republican Congressional support, the farm bill might be one of the few if only issues this year that brings Senators of both parties together to buck his veto with an override.

The farm bill underscores a broader issue that has plagued Congressional Democrats for months in dealing with the Bush administration. Democrats have long accused Bush of refusing to negotiate with them on key legislation, forcing lawmakers to draw their own conclusions about what he would sign into law. Pointing to the upcoming supplemental spending measure, for instance, Democrats privately say they are unclear about where Bush will draw the line.

Sen. Jack Reed (D-R.I.) acknowledged that Democrats are in a pickle as they look to close out the 110th Congress with accomplishments. But in his view, it’s because Bush remains unwilling to compromise. Reed said it is often “difficult to know where they are going,” adding that the only “real lever here is the public” to put pressure on Bush and the Republicans to come to the table.

But Senate and administration Republicans say their two-pronged bludgeon of the veto and filibuster is the best way to leverage bipartisan legislation in the remaining months of this Congress, most particularly on the supplemental that Democrats already have sought to pad with domestic items. Already Bush has hinted at a veto of that measure, and Senate Republicans said last week that they are likely to block the add-ons.

GOP Senators are aiming to force a replay of last December, when they won key concessions from Democrats on an alternative minimum tax fix, an energy package and a half-trillion-dollar spending measure.

“President Bush signaled last fall when we wrapped up the appropriations process what his position was. … They were going to be much more aggressive in disciplining spending and using the veto,” said Sen. Judd Gregg (R-N.H.), ranking member on the Budget Committee.

Gregg said the Republicans’ approach hasn’t changed since then, but he also believes Democrats don’t really mind if the worsening standoff between the two parties means few legislative proposals get done this year.

“Most of what they are doing is trying to position themselves with their constituents, not trying to legislate,” he said. “I suspect they don’t care if the president threatens to veto stuff.”

Sen. Lindsey Graham (R-S.C.), a close ally of presumptive GOP presidential nominee Sen. John McCain (Ariz.), said the challenges facing Democrats are of their own making, accusing them of locking minority Republicans out of the process by disallowing amendments and crafting legislation without them. He argued that Democrats “have made it impossible” for the Senate to make progress on common-sense policy this year, and said that if anything Bush — through his assertive use of the veto — has carved out an appropriate page in history.

“Maybe part of his legacy will be what didn’t happen,” Graham said.