ABRUPTLY -- so abruptly that the White House press office appeared not to know about it -- the administration withdrew its two witnesses, Homeland Security Secretary Michael Chertoff and Labor Secretary Elaine L. Chao, yesterday from today's Senate Judiciary Committee hearings on comprehensive immigration reform. No explanation was given. A better metaphor for the White House's inability to articulate an immigration policy would be hard to find: So divided is the administration that its leading members aren't even allowed to talk about the subject in public.

The absence of the administration won't diminish the significance of today's hearings, however. Despite the coming August recess and the Judiciary Committee's preoccupation with a Supreme Court nomination, four senators have now put their names on two serious pieces of immigration legislation. Pressure from them, as well as from a host of other senators from both parties who back immigration reform, seems to be pushing the issue forward. More to the point, the two bills provide a fairly good summary of where the sides in the immigration debate stand.

Both bills propose a guest worker program, tamper-proof forms of identity for all visa-holders and more money for border security. But the measure that will appeal most to the immigration restrictionists was introduced by Sens. Jon Kyl (R-Ariz.) and John Cornyn (R-Tex.). In essence, their bill would allow people to come from abroad and work here for up to two years before returning; would require illegal immigrants already here to return home before applying to join that program; and would add 10,000 new Border Patrol officers, 1,250 customs officers, more jail space and $5 billion worth of high-tech spending to improve border control.

Supporters of the opposing bill, introduced by Sens. John McCain (R-Ariz.) and Edward M. Kennedy (D-Mass.), believe the Kyl-Cornyn proposal is unrealistic. Mr. McCain points out that people who have been in this country for decades illegally will not go home voluntarily if they aren't convinced they'll be able to come back -- and that even if it worked, any program that abruptly ejected all 10 million estimated illegal immigrants could end up "wrecking America's economy." For that reason, the McCain-Kennedy bill requires illegals to pay a fine and back taxes and return to the back of the immigration queue, but it ultimately allows them to apply for legal status. The two senators argue that this is not an amnesty, because it requires a recognition of wrongdoing. They also argue that their bill, which creates a longer, more flexible temporary work visa, will encourage more people to cross the border legally. They are probably right.

It is possible, of course, that a compromise could be found, and indeed the outline of one is visible: It would contain high levels of enforcement; new funds for the borders and for identity cards; a realistic temporary visa program; and some means of legalizing those who are here without granting them a free pass. But no grand compromise will occur without political momentum and political leadership, from the strangely silent White House as well as Congress.