IF THE WHITE HOUSE IS finally serious about a comprehensive plan to fix the nation's immigration system, and there are signs that it is, then President Bush needs to get serious about working with Democrats -- and standing up to the more unreasonable members of his own party. Immigration reform is still possible this fall, but not without the president's bipartisan leadership.

This isn't the first time Bush has said he is ready to tackle the issue. He spoke about the need for reform in February 2001 and again in January 2004, each time raising expectations that he was prepared to remake the nation's immigration policies into a system that would be "safe, orderly and legal."

So it's reasonable to ask why this time is different. The answer is pleasantly surprising: Members of the House who were invited to the White House last week to hear the administration's proposal found it comprehensive. According to those present at the meeting, which included Rep. Jeff Flake (R-Ariz.), the plan is similar to a bipartisan bill introduced in Congress that has the strong support of both business and immigrant advocacy groups.

The president's proposal calls for better enforcement both on the border and in the workplace. It would also create a guest worker program that would be filled initially with those already working in the country.

The two main immigration bills currently in Congress, one sponsored by Sens. Edward M. Kennedy (D-Mass.) and John McCain (R-Ariz.) and another introduced by Sens. John Cornyn (R-Texas) and Jon Kyl (R-Ariz.) contain similar provisions.

Both bills call for better border law enforcement, stiffer sanctions on employers who hire illegal workers and a new electronic authorization system for verification of employment eligibility. They impose penalties on employers who fail to comply with the system. And both bills also call for giving applicants a temporary visa to work in the country, but they differ on a key provision. The Kennedy-McCain bill provides a path to permanent residency to workers who keep their job for six years and pay an application fee and a fine. The Cornyn-Kyl bill allows illegal immigrants to work for five years but then requires them to return to their own countries.

Bush should model his proposals along the lines of the enforcement provisions contained in the Cornyn-Kyl bill, and the legalization aspects in the Kennedy-McCain bill.

The president could also show his commitment to serious debate on this issue by dismissing some of the more ridiculous proposals from fellow Republicans such as Reps. Thomas G. Tancredo of Colorado and Tom DeLay and Lamar S. Smith of Texas, who favor strict enforcement first and a guest worker program second. Such partisans would prefer to seal the border and ignore or deport the 10-million-plus people already working here illegally.

Bush knows better than that. Ignoring those working here illegally won't fix the problem, and the notion that immigration agents can round up and deport 10 million people and their families isn't very realistic either.

If the president wants a safe, orderly and legal immigration system, he must be prepared to fight for reform that is both comprehensive and realistic. If he is truly ready to lead, he'll find the bipartisan support he needs in Congress.