WASHINGTON -- Both the Senate Republican leadership's unofficial agenda for the last pre-election session of the 109th Congress beginning this week and a privately circulated White House wish list are extraordinarily heavy. That means the planned adjournment date of Sept. 29 surely cannot be met, and even Oct. 6 may be too early. Yet, immigration is not mentioned on either expansive list.

This is remarkable because Republican members of Congress who talked to constituents during the August recess found the mood of the party's base remains as sour as it has been all year: unhappiness over too much government spending and unchecked illegal immigration under a Republican Congress and administration.

Republican Sen. Johnny Isakson, a moderate conservative who is a hard-liner on immigration, was quoted last week reflecting the consensus of his colleagues. Congress will do nothing about immigration until its lame-duck session after an election in which Republicans may well have lost congressional majorities. Isakson stated these reasons for inactivity: Congressional field hearings on immigration will not be concluded until mid-September, and intraparty GOP differences on the issue remain unsettled. The failure of Republican leadership on the issue of the year is palpable.

In the House at least, Speaker J. Dennis Hastert is trying to address immigration. He plans to bring together chairmen of the House field hearings later this week to see what can be done before the election. But House GOP sources say there is no chance of the party accepting a guest worker program that is integral to any compromise reform. The resolute House Judiciary Committee chairman, Rep. F. James Sensenbrenner, during the recess labeled as a "staggering burden on American taxpayers" the Senate-passed bill (approved by President Bush) because it contains the guest worker program.

Immigration is the most melancholy element of a depressing Republican year. The Iraq intervention and its aftermath have hurt, and Republican inattention to runaway government spending has been deplorable. But immigration is the issue most likely to cause rank-and-file Republican voters to stay home on election day, and it may cost the party its congressional majorities.

When Republican Rep. Mike Pence went home to his east central Indiana district in August, he found constituents upset -- as they had been all year -- about spending and immigration. Chairman of the conservative Republican Study Committee, Pence has courageously taken the position that a border security bill should not omit a guest worker program (that does not include a path to citizenship).

Pence, a rising star in the conservative movement, has faced a torrent of right-wing abuse for advocating a guest worker program that is condemned as amnesty for illegal aliens. Rep. Tom Tancredo, leader of the congressional hard-liners on immigration, has viciously branded Pence as an apostate. But Pence told me last week that Hoosier voters, when he explains it to them, will accept his three-part formula on immigration: protect the border, no amnesty for illegals and access for foreign workers needed by the U.S. economy.

Although no more than 25 House Republicans follow Tancredo's rigid line, that is enough to obstruct a coherent Republican posture. But many more conservative lawmakers write off any guest worker program as just amnesty. In trouble on Iraq and federal spending, Republicans are being lured into a nativist posture that is political fool's gold.

George W. Bush, John McCain and Mike Pence dread a Republican descent into nativism. In my half century of political reporting, I never have seen a candidate or party succeed in playing the economic nationalist card. Even worse, a divided party promises to go into the hazardous 2006 election after doing nothing about an issue its constituents think is most important.

"You get it!" Bush earlier this year told Pence after he agreed with the president that permitting new immigration is compatible with protected borders. "I not only get it, I lived it," the congressman replied, telling him of his grandfather, Mike, who emigrated from Ireland in 1923 and became a Chicago bus driver. Pence told me last week from Indiana he will try to make something happen in the September session. It is an uphill climb, but the grim alternative is a divided Republican Party going into this election campaign with a blank slate on immigration.