The Senate is headed into a politically charged debate on the effect of the troop surge in Iraq.

Aides predicted the Senate will vote Tuesday on an amendment to the fiscal 2009 defense authorization bill (S 3001) offered by Joseph I. Lieberman , an independent from Connecticut, that includes language touting the success of the troop buildup that began last year.

A vote is also likely on an alternative to be filed by Democrats Carl Levin of Michigan and Jack Reed of Rhode Island that would offer a more nuanced assessment of the security situation in Iraq.

The timing of the votes could slip later into the week as Democratic and Republican leaders attempt to reach agreement on how many amendments to the defense bill will be considered.

The Lieberman amendment, backed by numerous Republicans, would “recognize the success of the troop surge . . . in particular as a strategic victory in a central front in the war on terrorism.”

In an apparent allusion to Democratic attempts to set a timeline for withdrawing U.S. combat forces from Iraq, the amendment also says, “It is imperative that no action be taken that jeopardizes those gains or dishonors the service and sacrifices of the men and women of the United States armed forces who made those gains possible.”

The Levin-Reed alternative will declare that the surge has been a tactical, not strategic, success, that al Qaeda’s presence in Afghanistan and Pakistan poses a greater threat than that of insurgents in Iraq and that the Bush administration does not have an effective strategy to defeat al Qaeda or win the peace in Afghanistan.

“The current demand for forces in Iraq and Afghanistan exceeds our sustainable supply of soldiers, of units and equipment, and limits our ability to provide ready forces for other contingencies,” the amendment reads. “Our readiness, quite frankly, is being consumed as fast as we can build it.”

The debate over the surge will be conducted in the heated atmosphere of a presidential campaign. Lieberman is backing the Republican nominee, Sen. John McCain of Arizona, who supported the surge from the outset and credits it for the decline in violence in Iraq.

McCain’s Democratic opponent, Sen. Barack Obama of Illinois, opposed the surge. Obama recently called the troop increase one of several factors that have reduced violence in Iraq. He also cites a Sunni alliance with U.S. forces against al Qaeda in Iraq and a decision by Shiite militias to halt their attacks on U.S. forces. But Obama says the surge has not contributed to political progress in Iraq and has diverted military resources needed in Afghanistan.

Republicans, who accuse Obama of poor judgment on the surge in 2007, want to force Senate Democrats to take a stand on the issue. Although Obama may not be present for the Senate vote, he is bound to be asked on the campaign trail how he would have voted.

Lieberman’s role in setting up a partisan debate on the surge has contributed further to tensions between the former Democrat and Senate Democrats, tensions that heightened when Lieberman addressed the Republican convention on McCain’s behalf.

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