A bill that would give Washington, D.C., a full vote in the House took another small step forward Tuesday, as lawmakers, legal experts and civil rights advocates testified in favor of the measure before a Senate committee.

But constitutional concerns surrounding the legislation remain, and supporters admitted they have much work left to do to get the votes necessary to avoid a filibuster.

Sponsored by Sen. Joe Lieberman (ID-Conn.) and Utah Sens. Orrin Hatch (R) and Bob Bennett (R), the D.C. House Voting Rights Act would give the District a full vote in the House while also granting a fourth Congressional seat to Utah, which just missed getting another Member after the 2000 Census.

At the Tuesday hearing of the Lieberman-chaired Homeland Security and Governmental Affairs Committee, the Connecticut Senator said he plans to bring up the bill in committee for a markup in the first weeks of June, giving Members “time to consider all the arguments.”

“We are going to try and move this bill through the committee and out to the Senate floor as soon as we can,” Lieberman said.

Other Members voiced their support. Sen. Claire McCaskill (D-Mo.) told the panel she plans to sign on as a co-sponsor, and Lieberman said Sen. Mark Pryor (D-Ark.) promised to do the same. Democratic Sens. Mary Landrieu (La.) and Barack Obama (Ill.), who also sit on the committee, already have signed onto the bill as co-sponsors.

Judiciary Chairman Patrick Leahy (D-Vt.) is another co-sponsor, along with five other Senators. But to get the bill through the chamber, supporters will need to get at least 10 Republicans on board, supporters said, and there appears to be strong opposition among non-Utah Republicans.

Senate Minority Leader Mitch McConnell (R-Ky.) has called the bill unconstitutional, and the Senate Republican Policy Committee cited problems with the House version in a March memo.

For her part, Governmental Affairs ranking member Susan Collins (R-Maine) told the panel that while she is a supporter of voting rights for D.C., she has concerns about the constiutionality of the current measure, and she stopped short of giving it her backing.

“If Congress can constitutionally pass legislation to grant the District a fully empowered Member of the House of Representatives, I would support that measure,” Collins said. “If, however, legislation granting the District a voting Representative in Congress violates the Constitution, then it will fail as surely as if we attempted to suspend the right of free speech.”

One constitutional concern that was brought up by Republicans in the House appears to be remedied in the Senate measure. In the House version of the bill, which passed in a 241-177 vote in April, Utah would receive an at-large seat, avoiding the need for the state to undertake a mid-decade redistricting process.

But Hatch and some critics had concerns with that structure, since it would mean every Utah resident would be represented by two different House Members. So, in the Senate version, Utah would redistrict and the new Representatives would take office in the 111th Congress, avoiding the need for a special election.

“I insisted that Utah be required to redistrict to provide for the new seat,” Hatch said. “I believe that Utah’s legislators deserve the freedom to determine their Representatives’ districts without unjustified intrusion or mandate of the federal government.”

Rep. Tom Davis (R-Va.), who originally crafted the D.C.-Utah compromise, gave his support to the change Tuesday, telling the panel he had “no problem” with the fourth district option.

Eight witnesses testified before the committee. On the first panel, Hatch, Davis, D.C. Mayor Adrian Fenty (D), and Del. Eleanor Holmes Norton (D-D.C.), who co-sponsored the House bill with Davis, testified in favor of the measure.

On a second panel, former Rep. Jack Kemp (R-N.Y.), Wade Henderson, the president of the Leadership Conference on Civil Rights, and Georgetown law professor Viet Dinh, the former assistant attorney general who helped craft the USA PATRIOT Act, all spoke in favor of the bill.

George Washington University law professor Jonathan Turley was the only opposing witness, saying the measure is blatantly unconstitutional because the Constitution only allows states to be fully represented in Congress.

“As moving as the testimony has been, do not dismiss the significance of what you are about to do,” Turley said. “You are about to manipulate the size of Congress.”

Turley added that future Congresses could use this action as precedent for expanding the House in improper ways.

“This is, and always has been, not a question of ends, but of means,” he said. “There are many ways to correct a historic wrong, but it’s not always easy.”

Others argued that the Constitution’s District Clause, which allowed Congress to extend taxes and court matters to the District, provides a Congressional remedy to the voting rights issue.

“The founders knew there would be unforeseen problems created in the ratification and everyday use of the Constitution,” Davis said. “In the District Clause, they gave Congress the flexibility to solve those kinds of problems. All that’s lacking is the will to solve them.”

In a passionate oratory, Kemp said the bill provides an opportunity for the Republican Party to return to its civil rights roots, referring to the GOP as the party of Abraham Lincoln and pointing to former President Dwight Eisenhower’s decision to send troops to Arkansas to integrate public schools.

“Our party had a great history, Sen. Collins, and we walked away from it,” Kemp said. “We can’t walk away from this. … I’m putting the party on the spot.”

Norton spoke about the overall D.C. voting rights effort, pointing to the civil rights movement and her personal family history as background for the current measure.

“The only real obstacles to [passage] are political,” Norton said. “Yet, this is one of those moments I believe that democratic principles can prevail.”

The D.C.-Utah compromise provides a unique way for Congress to spread democracy, Norton added.

“This bill was born bipartisan, and it wasn’t born on my side of the aisle. It was born with my right-hand here,” Norton said, pointing to Davis, who crafted the D.C.-Utah compromise.

Norton also joked about the two Members’ past appearances on The Colbert Report. While host Stephen Colbert mocked Norton’s lack of representation the four times she appeared on the show, Colbert asked Davis if the voting rights bill is proof he is having an affair with Norton.

“If there is any such thing as a political affair, I think I plead guilty,” Norton joked, drawing laughter.

Following the hearing, Ilir Zherka, executive director of the advocacy group DC Vote, said he is optimistic the bill is on the right track.

“Today was a victory for D.C. voting rights, because not a single Member of the panel came forth saying D.C. residents didn’t deserve a vote,” he said.