Earmark foes are preparing to force a vote that would oblige senators to disclose all campaign contributions connected to their pet projects.

As the battle over the budget heats up, Sen. Tom Coburn (R-Okla.) and other senators are readying an amendment in case Democrats propose an alternative to a Republican-led moratorium on earmarks, as Coburn suspects.

The debate will hit a peak Thursday when all three contenders, Sens. John McCain (R-Ariz.), Hillary Rodham Clinton (D-N.Y.) and Barack Obama (D-Ill.), are expected on Capitol Hill to vote on a one-year earmark moratorium. A long amendment process may push the vote into late Thursday or Friday, however, which could conflict with the candidates’ campaign plans.

All three presidential candidates support the moratorium contained in an amendment from Sen. Jim DeMint (R-S.C.). But it has drawn sharp criticism from senior Democrats and Republicans, who say it is Congress’s constitutional duty to set the country’s funding priorities. Senior Democrats have discussed an alternative that would instead allow earmarks but make them more transparent.

Opponents of earmarks say the practice, which has grown, caused congressional corruption scandals and wastes taxpayers’ money. Democratic plans are a smokescreen, these opponents say.

If Democrats offer their transparency plan, Coburn may offer his amendment, GOP aides say.

“Any new ‘transparency’ measure that doesn’t require members to immediately disclose campaign contributions associated with their earmarks will be a total fraud,” a Senate Republican aide said.

“There’s a reason Jack Abramoff called the Appropriations Committee the ‘earmark favor factory,’ ” the aide added, referring to the infamous lobbyist jailed for corruption in 2006.

The Coburn plan would apply to new earmarks and past campaign contributions, the aide said. For instance, a senator would have to disclose campaign contributions from employees of a company that would receive earmarks. How far back the amendment would apply has not been decided, but the measure has been actively discussed by a group of senators, according to the aide, who would not disclose names.

Considering the amendment could be risky for lawmakers. Opposing the measure could open senators up to charges of endorsing the trading of taxpayer dollars for campaign contributors.

Senate Budget Committee Chairman Kent Conrad (D-N.D.) said Wednesday the “devil is in the details” with respect to Coburn’s amendment, which would be offered to a fiscal 2009 budget blueprint. But Conrad said it “doesn’t sound unreasonable to me.”

Conrad is working with Democrats on their own transparency amendment, but he said it wasn’t clear whether such a plan would be offered or who would offer it.

Senate Majority Leader Harry Reid (D-Nev.), who strongly opposes the DeMint amendment, said Wednesday he wasn’t sure whether there is enough opposition to defeat the moratorium this week.

The amendment will likely need 60 votes to overcome a point-of-order stating that it is not germane to the budget resolution.

“The vast majority of Democrats will recognize this as a publicity stunt,” Reid told reporters Wednesday. “Keep in mind, last year — led by nine new energetic Democratic freshmen — we changed ethics and lobbying rules significantly.”

Reid said last year’s ethics law provided “total transparency” of the process by requiring legislation for the first time to specify who the authors of each earmark were.

“As we look back in history, the Founding Fathers would be cringing to hear people talking about eliminating earmarks,” Reid said, noting that the Founders dictated in the Constitution that all spending should originate in Congress, not the executive branch.

Other Republicans have been cool to DeMint’s plan as well, including Sen. Judd Gregg (N.H.), the Budget Committee’s ranking Republican, and Minority Leader Mitch McConnell (Ky.), a longtime top appropriator. McConnell would not say Wednesday how he would vote on the DeMint measure.

Gregg called an outright ban on earmarks “an abolition of the authority of Congress.”

“And it basically passes to the executive branch massive amounts of authority, which I’m not sure you want to embed in a bureaucracy which is unaccountable,” he said. “At least members of Congress are accountable.”

Elsewhere Wednesday, Democrats opened a new front in the ongoing budget battle by accusing Republicans of “short-changing” veterans’ healthcare. The Democratic-written budget, which is non-binding, includes $3.2 billion more than President Bush’s request for health programs at the Veterans Administration.

“The funding level provided in this budget resolution is a first step towards ensuring these men and women get the care they need,” said Sen. Daniel Akaka (D-Hawaii), a World War II veteran.

Sen. Charles Schumer (D-N.Y.) said the Bush administration is spending $430 million a day in Iraq but is unwilling to support soldiers when they return.

“The president has effectively told the troops, ‘You must take care of us, but we will not take care of you,’ ” Schumer said.

McConnell spokesman Don Stewart said Bush’s budget isn’t before the Senate and that senators from both parties will have the opportunity to address the issue of veterans’ care during Thursday’s budget voting.