With Rep.-elect Bill Foster (D-Ill.) set to be sworn in as early as today, GOP millionaire Jim Oberweis and Republican Party insiders are reconsidering their general election approach following Saturday’s humiliating defeat to serve out the remainder of former Speaker Dennis Hastert’s term.

Oberweis’ campaign on Monday backed away from its earlier blank-check claims, telling Roll Call that the dairy magnate will not spend more than $2.5 million ahead of the Nov. 4 general election. The GOP candidate, who has now lost four expensive campaigns since 2002, said in December that he will “spend whatever it takes to win.”

To date this cycle, Oberweis has given his campaign $2.34 million, according to Federal Election Commission records. The National Republican Congressional Committee also ponied up one-fifth of its available cash, $1.24 million, to try to retain the seat.

The NRCC, Oberweis’ campaign and Republican operatives throughout the state on Monday shied away from discussing Saturday’s loss on the record.

But as Republicans licked their wounds on Monday, computer servers for the Democratic Congressional Campaign Committee and Democratic House hopefuls hummed in the wake of Saturday’s unexpected win.

Consultant Dan Seals (D), whose candidacy — like Foster’s — is piggybacking on the popularity of home-state presidential candidate Sen. Barack Obama (D), passed the virtual hat Monday for his race against his rematch with well-financed Rep. Mark Kirk (R-Ill.).

“This weekend Illinois voters sent a clear signal to Washington that they are ready for change,” Seals wrote in a fundraising e-mail blasted out on Monday. “Bill Foster’s victory in IL-14, a traditionally Republican seat formerly held by Dennis Hastert, sent shockwaves through the political establishment and showed the pundits that Illinois is ground zero in the movement for a new direction that is sweeping the nation.”

As Democrats reveled, however, Republicans in Illinois and elsewhere on Monday grumbled privately about the loss and warned against looking too closely into the race. Still, party insiders say the blame for Saturday’s symbolically disappointing defeat lies squarely with Oberweis. Despite his chain of popular, eponymous Chicago-area ice cream stores, Oberweis has proved to be unpopular with district voters because of his salty demeanor and scorched-earth campaign style, these insiders said.

“Central to the problem is him,” an Illinois Republican source said on Monday. “He’s going to have to recognize that he has a likability problem in the district. Until he does, nothing is going to happen — people don’t like him.”

The GOP source pointed to troublesome preliminary election data out Monday that suggest heavy Republican crossover voting in the district.

In suburban Kane County, the source said, 20 percent to 30 percent of Republicans turned out and roughly 13 percent of Democrats showed up in the parties’ 20 top precincts.

“The problem was [the Republicans] voted for Bill Foster,” the source said. “The ground game was there. … They just don’t like Jim Oberweis.”

Republicans on Monday stopped just short of calling for Oberweis to abandon a November do-over for a full two-year term. Party insiders, however, are encouraging Oberweis’ camp to think seriously about its current strategy and staff lineup.

“What’s the definition of crazy? Doing the same thing over and over again and expecting a different result,” said an Illinois Republican source.

“You need a candidate that’s willing to recognize that he has a likability issue,” the source continued.

An Oberweis campaign source disputed local Republicans’ claims of widespread party-switching in Saturday’s special election, saying that “the other side got more voters to the polls.”

“We’ve got to wait for the county clerks to gather the information on who showed up to vote,” the source said. “Knowing who showed up to vote is going to help us determine whether this a failure of organization or a failure of communications.”

“If it turns out that an equal number of Republicans and Democrats showed up to vote and we got beat, then it’s a function of messaging,” the source continued. “If more Democrats showed up than Republicans, then that’s a function of organization — we failed to turn out our vote.”

The Oberweis campaign source also said that “no decisions have been made” about staff shake-ups, while adding, “There’s been no discussion of Jim taking his name off the ballot.”

And with Foster now the incumbent, Oberweis’ campaign and other Republicans said their November strategy likely will focus on Foster’s “tough votes in a Pelosi-led Congress” in a district Republicans still consider their home turf.

“He basically ran a campaign where he tried to be all things to all people and tried to keep the focus on ‘Oberweis is a bad guy,’ ” a Oberweis campaign source told Roll Call. “And you know what, he was successful in running that campaign.”