Debate starts up today in the U.S. Senate on the pending comprehensive immigration reform bill. U.S. News has a brief summary of the current situation in this online article. Excerpts:

Here they go again. The Senate is about to engage in another round of the seemingly endless fight over America’s immigration laws. It’s officially the members’ second shot in the past month at pushing through a “grand bargain” piece of legislation that tries to give a little to every interest group while not entirely satisfying any of them. A compromise, they say.

The debate kicks off on Tuesday with a procedural vote just to get the full debate underway. It’s been that kind of step-by-step battle all along for an unlikely trio in arms: President Bush, Democratic Sen. Edward Kennedy of Massachusetts, and Republican Sen. John Kyl of Arizona. And no one is absolutely certain the Senate will pass that first test. Some conservatives opposed to the bill say support is eroding.

If the procedural hurdles are overcome, however, the road to change there on out will be anything but smooth. It’ll take a great deal of legislative handiwork and backroom wheeling and dealing to get through this week before the July 4 recess with a bill in hand. “This is a complicated bill,” says Joel Kaplan, deputy chief of staff for policy at the White House. “It’s taken some time for people to understand what’s in there.” Talk about an understatement. Cabinet Secretaries Carlos Gutierrez of commerce and Michael Chertoff of homeland security have become virtual tenants up on Capitol Hill, pushing and prodding recalcitrant senators.

The pivot points?

*The Bush administration has included $4.4 billion in border security funding as a sweetener to its Republican brethren worried about law, order, and enforcement. Whether that shifts votes remains to be seen.

*For the high-tech business community, the linchpin is an amendment pushed by Sens. Maria Cantwell of Washington and Kyl of Arizona. It would give employers more flexibility in whom they hire and would increase the number of visas for skilled workers by 40,000. The business community was opposed to the bill in its earlier incarnation, and if this amendment fails, look for high-tech corporations to back away.

*Other key issues to watch will be whether there is any sort of provision in the bill that makes family reunification a key part of immigration policy and whether an amendment passes that requires a “touchback provision” for illegal immigrants who want legal status to return to their home countries.

What all that means for the bill’s ultimate fate is unclear. “There are so many moving pieces,” says Kara Calvert of the Information Technology Industry Council, a Washington industry group. “So many people are reserving whether they’ll vote for it.”

Part of the thinking of the bill’s chief backers is that they just need to get the process rolling and that once they get the debate underway in the Senate, they’ll have time to renegotiate troubling pieces. Looking down the road, they think they’ll buy themselves time to modify the bill in the House of Representatives–even though its fate there is especially unclear and a bloc of “amnesty”-rhetoric opponents awaits–and then even later when the House and the Senate try to come together with one piece of legislation to send to the president.