The "Gang of Eight" comprehensive immigration reform bill cleared an important obstacle Tuesday night when the Senate Judiciary Committee passed the plan -- without significant changes -- to the full Senate for consideration.

The committee approved the legislation, 13-5, and chairman Sen. Patrick Leahy, D-Vt., praised the transparency of the debate.

"I don't think there has been a markup on such a complex bill that has been this open," Leahy said. "The dysfunction in our current immigration system affects all of us and it is long past time for reform. I hope that our history, our values, and our decency can inspire us finally to take action."

The committee rejected dozens of attempts to amend the bill and left the essence of the plan intact: a path to citizenship for the 11 million unauthorized immigrants in the country, more visas for immigrants in the STEM fields and measures to increase border security.

Leahy attempted to add an amendment that would have added protections for same-sex immigrant couples. But Leahy dropped the idea when Republicans, including members of the Gang of Eight, threatened to withdraw support for the bill if same-sex provisions were included.

The committee vote clears the way for what figures to be a historic floor fight in the Senate. Majority Leader Harry Reid, D-Nev., says he will bring the bill up for debate early next month and it could take weeks for senators to decide its fate.

The Heritage Foundation, a Washington-based conservative think tank, released a report this month -- written by Jason Richwine and Robert Rector -- that projects a $6.3 trillion federal price tag for the comprehensive immigration reform plan Congress is considering.

The report (it's hardly appropriate to call it a study because it's so one-sided and poorly researched) maintains that over 50 years, the 11 million unauthorized immigrants who would be legalized by the reform plan will consume more in federal benefits than they will pay to the government in taxes. But the authors didn't bother to fairly assess the contributions immigrants and their families will make to society and the U.S. economy over the half-century.

Republicans and Democrats alike have criticized the report's methodology, or rather, the lack of it.

Neither the Heritage Foundation nor the authors have much credibility when it comes to useful evaluations of immigration policy.

Six years ago, the foundation came out with a similar report with similar deficiencies when Congress was considering another immigration reform bill. The recent offering from Heritage seems like leftovers from a bad meal.

As for Richwine, he resigned from Heritage last week after racially charged comments surfaced from his past. In his dissertation for a doctorate from Harvard, Richwine asserted that the average IQ of immigrants in the United States is "substantially lower than that of the white native population."

A bipartisan group of U.S. House members working on comprehensive immigration reform legislation has agreed on a 15-year path to citizenship for unauthorized immigrants, two years longer than the 13-year proposal in the Senate plan.

Many Democrats and immigrant advocates, who complained that the Senate's proposal by the "Gang of Eight" was too long to wait, are of course more negative about the longer wait the House wants.

But negotiators say they need 15 years to get enough support among Republicans to keep the legislation alive.

Both House and Senate proposals require a 10-year wait before an unauthorized immigrant could apply for permanent legal status and get a green card. The wait for citizenship after that is the latest sticking point.

Immigrant advocates worry that if the wait becomes too long, the incentive is diminished for immigrants to come out of the shadows and participate in any legalization program.

Would a 15-year wait for citizenship defeat one of the main purposes of comprehensive immigration reform? Does it replace an illegal limbo for immigrants with a legal one where the penalties outweigh the benefits? What good is reform for 11 million unauthorized immigrants if they lose reasons to participate and then don't?

These are hard questions that Congress members can't answer with their political dealmaking that considers partisan point-scoring and not real-life consequences.

The Gang of Eight's proposed comprehensive immigration reform bill has started its formal journey through Congress, and already there have been volleys of poison-pill amendments intended to derail the legislation as it goes through the Senate's committee mark-up process.

Complaints from Republicans on the far right, including Tea Party favorite Sen. Ted Cruz of Texas, are that the proposal doesn't do enough to stop illegal traffic across the U.S.-Mexico border. Cruz proposed an amendment that would triple the number of Border Patrol agents to 60,000 and greatly increase border surveillance equipment. His amendment was voted down in committee however.

On the left, Sen. Chris Coons, D-Del., offered a proposal that would prevent Homeland Security Secretary Janet Napolitano from deporting unauthorized immigrants to dangerous areas in their homelands. That proposal also died.

Sen. Marco Rubio, R-Fla., one of the Gang of Eight leaders, says there's room for improving the bill and that he's "encouraged that we are witnessing a transparent and deliberate process" to get it amended and passed.

The path to citizenship and ensuring a more secure border (a so-called "border trigger") with Mexico remain the two major potential stumbling blocks for passage.