After the completion of ballot counting in each county of the district, Bean said she called Walsh Tuesday night on her return to Illinois and congratulated him on his election.
Walsh had a nearly 300-vote lead over the Democratic incumbent earlier Tuesday, according to unofficial vote totals released by three counties.
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Walsh, a tea-party backed candidate, had 98,115 votes in Cook, Lake and McHenry counties, compared with the three-term incumbent's 97,825. Tuesday was the deadline for absentee ballots to arrive; provisional ballots were also included in the counts.
The Palatine Tea Party issued a statement late Tuesday calling Walsh's victory "a huge win for all the grassroots organizations that supported Walsh."
Republican National Committee Chairman Michael Steele also issued a statement on Walsh's victory.
"I would like to congratulate Representative-elect Joe Walsh for his victory today in Illinois' Eighth District Congressional race. Although it took a few weeks to count all the votes, Illinoisans made their voices heard that they will no longer tolerate the reckless big government, tax and spend policies in Washington," Steele said.
Both Bean and Walsh were in Washington on Tuesday.
Walsh declared victory shortly after the Nov. 2 election. His win means the state's 19-member congressional delegation will have 11 Republicans, contributing to the state's first GOP majority for Illinois in seven years.
In Lake County, Walsh had 55,148 votes compared with Bean's 52,026, according to updated results on Lake County's clerk website. In McHenry County, Walsh had 19,119 compared with Bean's 15,774, according to the clerk on Tuesday evening. In Cook County, Walsh had 23,848 votes compared with Bean's 30,025, according to Cook County Board of Elections spokeswoman Courtney Greve.
Election authorities in those counties have a Nov. 23 deadline to certify results with the Illinois State Board of Elections.
On Election Day, Illinois mirrored national trends with voter discontent and a national anti-incumbency mood contributing to Republican wins, including Republican Mark Kirk's win over Democrat Alexi Giannoulias for President Barack Obama's old U.S. Senate Seat.
Still, the close election in the northeastern Illinois congressional district took many by surprise as Walsh's congressional bid had troubles early on and national Republicans refused to fund his campaign.
"Everybody would admit that it was a race that wasn't on anybody's radar," said Illinois Republican Party chairman Pat Brady. "We made a mistake."
The other issues included a campaign manager who quit and then sued Walsh for $20,000 in nonpayment and two more staffers who quit and accused him of not properly disclosing a 2008 home foreclosure and traffic citations to the public.
Unlike other Republicans who won districts held by Democrats on Nov. 2, Walsh didn't receive an invitation to the National Republican Congressional Committee's "Young Gun" programs.
They included political newcomer Bobby Schilling who defeated two-term Democrat Rep. Phil Hare in the 17th District, Republican Adam Kinzinger who beat first term Democratic Rep. Debbie Halvorson in the 11th and Republican state Sen. Randy Hultgren who beat Democratic Rep. Bill Foster in the 14th.
The 8th District, which covers many wealthy communities, had been largely Republican until 2004, when Bean unseated Republican Rep. Phil Crane.
Democratic state Sen. Terry Link, who is chairman of the Lake County Democratic Party, said the congressional race was close because independents voted Republican.
"It was the national wave that caused it to be close," he said. "It's quite unfortunate."
Walsh has never held public office but has tried before: He ran unsuccessfully for Congress in 1996 and for the Illinois House in 1998.