The Senate bogged down Wednesday over competing efforts to investigate how a $10 million earmark for a road in Florida was slipped into a highway bill that had passed both chambers.

A tough-talking Sen. Barbara Boxer (D-Calif.) said people “ought to go to jail” for the maneuver — and said her approach would result in that. She pushed her amendment that would call on the Justice Department to investigate the matter.

In a spirited debate, she squared off against Sen. Tom Coburn (R-Okla.), who said the Senate should police itself and called for a bipartisan, bicameral committee to find out what happened.

The Boxer-Coburn debate has been the focus of the highway technical corrections bill, which would remove the $10 million earmark. Rep. Don Young (R-Alaska), the former chairman of the Transportation and Infrastructure Committee, is believed to have played a role in inserting the earmark for the Coconut Road project near Fort Myers, Fla. The road would benefit a developer in Florida who raised money for the lawmaker.

Coburn’s amendment has drawn bipartisan support, including from Florida Sens. Bill Nelson (D) and Mel Martinez (R) and presidential hopefuls Sens. Hillary Rodham Clinton (D-N.Y.), Barack Obama (D-Ill.) and John McCain (R-Ariz.).

Earlier in the day, Boxer, chairwoman of the Environment and Public Works Committee, broke off indirect talks with Coburn, contending that his approach would result in a “political circus” that would undermine any of the investigation’s findings and inject politics into a potentially criminal manner.

“I think it’s very possible people ought to go to jail here. A Senator and a House Member can’t send people to jail. I think this is a much better way to go — it keeps politics out of this. If there was a crime, then the person ought to go to jail, the people ought to go jail,” Boxer said.

“They’ll call hearings and the press will come. I can just see this thing. I want to avoid a circus. I want to put somebody in jail if there was a crime. What I want is justice done. I don’t want political theater,” she added.

Coburn argued that Congress should police itself. “I believe in the people in this body. I believe that we all don’t like this happening. The best way to do this is to have an investigation. My worry is if we modify this amendment, or we don’t pass this amendment, is this political? Can we not control the rules of our own body?” he asked.

The oratorical outburst from two of the Senate’s polar opposites — Coburn is one of its most conservative lawmakers, while Boxer is one of the most liberal — followed nearly 24 hours of talks between Coburn and Environment and Public Works ranking member James Inhofe (R-Okla.), who acted as a go-between for Coburn and the Democrats.

Boxer, Senate Majority Leader Harry Reid (D-Nev.) and Speaker Nancy Pelosi (D-Calif.) oppose Coburn’s amendment, as well as an earlier proposal Coburn and Inhofe floated to have the Government Accountability Office conduct the investigation. Boxer, who also heads the Ethics Committee, said the Senate should not be in the position of investigating a House Member, which she said would violate the Constitution.

Coburn said it was not a given that the probe would involve a House Member — that, he said, was speculation. He said the Senate should get to the bottom of the matter.

During a midday vote on a motion to recommit the bill offered by Sens. Jim DeMint (R-S.C.), Coburn, Reid, Boxer, Nelson, Ted Stevens (R-Alaska) and other lawmakers and staff huddled on the Senate floor in a last-ditch effort to find middle ground, sources said.

But those discussions quickly collapsed, and Coburn eventually offered his amendment, touching off the Boxer-Coburn face-off. In the end, Boxer and Coburn both proposed their own competing amendments, with Coburn pursuing his original language while Boxer proposed a “Sense of the Senate” resolution calling on Justice to conduct an investigation. A vote on the amendments could be this week.