Early results show Illinois Sen. Mike Jacobs ahead of Republican challenger Bill Albracht.
Sen. Jacobs has 24,216 votes to 20,085 for Mr. Albracht after early tallies from Rock Island, Whiteside and Carroll counties.
Sen. Jacobs has 16,014 votes to Mr. Albracht's 12,829 in Rock Island County with 26 of 120 precincts reporting. He has 6,017 votes to 4,546 for Mr. Albracht in Whiteside County with 29 of 57 precincts reporting. Sen. Jacobs has 606 votes to Mr. Albracht's 346 with 8 of 8 precincts reporting in Carroll County. In Henry County, Sen. Jacobs had 1,975 votes, slightly fewer than Mr. Albracht's 1,983.
Democrat Brian Vyncke has been elected in Rock Island County Board District 8, taking 61 percent of the vote to Republican Jim Gager's 38 percent with all four precincts reporting.
Elsewhere, Republican Bob Westpfahl has been elected in district 25 with 57 percent of the vote to Democrat Mark Williams 42 percent with all 6 precincts reporting.
Republican hopes of taking control of the county board for the first time since 1972 are fading. Democrats are leading in 22 of the 25 races so far.
Rock Island County Republicans and Democrats, gathered at two huge parties in downtown Rock Island, are both sounding confident as they wait for results to trickle in.
Democrats have been buoyed by talk of a large turnout on the west side of Rock Island, territory they say heavily favors their candidates.
Rock Island County Board member and Democrat Virgil Mayberry said there were long lines at the Martin Luther King Center when polls closed at 7 p.m.
"We've never seen that many people," he said. "There were people waiting over an hour and I believe it's a great sign for our president and Cheri Bustos."
Rock Island County Republican Party Chairwoman Susie Carpentier, however, said from what she's seen so far turnout across the county seems to be down from the 2008 presidential election.
"I think we are going to do really well tonight," she said. "This is the biggest election night party we've ever had."
Republican candidates are gathered at the Stern Center in the refurbished Hyman Furniture building. Democrat Cheri Bustos and other Democratic candidates are gathering nearby at the Holiday Inn in Rock Island.
Nearly 21,000 people voted in Rock Island County by 2:30 p.m., with 67,000 to 68,000 expected before the polls close, Rock Island County Chief Deputy Clerk John Brown said.
More than 70,000 voters would set a record, he said.
The heaviest voter turnout by 2:30 p.m. was in the west end of Rock Island, where 40 percent of expected votes were tallied, Mr. Brown said.
No major problems had been reported, he said.
Mr. Brown said he was unaware of discrepancies on a voting center list on the county clerk's home page.
Voters were waiting when polling places opened Tuesday, and the heavy pace continued in what election judges and a poll watcher described as one of the best turnouts they've seen in years.
In the first three hours, more than 400 people voted at Moline's First Christian Church, election judge Taryn Hancock said. About 45 people were waiting when she announced at 6 a.m. that ''OK, the polls are open.''
Long lines kept forming and the church parking lot at 1826 16th St., Moline, stayed full.
''Everyone was eager to cast their vote,'' Ms. Hancock said.
It was no different at seven other Moline and Coal Valley precincts, according to poll watcher Justin Anderson. ''Judges are commenting of how unusually busy they are,'' he said.
It's his fifth election cycle as a poll watcher, and he said he's never seen it busier, but wasn't surprised by the turnout.
About 20 people were lined up in front of Rock Island Township Hall, 2827 7th Ave., Rock Island, and more than 225 voters had cast ballots by 10:20 a.m., election judge Irma Gripp said.
At the Martin Luther King Center in Rock Island, 300 to 400 voters were counted by 10:30 a.m., election judge Della Perkins said.
More than 20 people were waiting for the doors to open at the South Moline Township Senior Center, at 637 17th Ave., East Moline, election judge Tiffany Holmes said.
''It's been steady ever since,'' she said, with 565 voters counted by 11 a.m.
''We like to have fun here, so we try to predict how many people will vote,'' Ms. Holmes said. "We're predicting between 1,700 to 2,000."
By 11:30 a.m., 471 voters had made their way to the polling place at Riverside Garden Center, at 3400 5th Ave., Moline, election judge Don Fey said.
'"We've averaged about 90 per hour,'' he said.
He has been an election judge for the past 20 years, and declared ''this is as good as it gets."
Alfred Oien, of Moline, spent the morning at First Christian Church ''people watching,'' he said. It wasn't his polling place. He was waiting for his wife to finish working at the church's daycare. But he said it was the most voters he's remembered seeing since 1967.
Brandon Van Kauren of Moline rode his KHS Flite road bike in the rain to vote at the church.
''I didn't have to fight for a parking place this way,'' he said. He already had taken care of some banking business, and stood at the church entrance in the rain before getting into the church to vote and opening the door for other voters.
Ms. Gripp at Rock Island Township Hall said she was thankful it wasn't rain when she was carrying supplies in at 4:30 a.m.
A news crew from WREX-Channel 13, from Rockford, came to the Martin Luther King Center, to air reports about the 17th Congressional District race.
''Rockford's new to the 17th, and is a highly touted race,'' reporter and weekend news anchor Matt Groves said.
An election judge at the King Center announced at one point that "We're getting a lot of people who are not registered to vote here. Look on the back of your registration cards to see if you're supposed to be voting here or not."
People not knowing or realizing their polling place had changed was a recurring problem Tuesday, but not a major one, Ms. Hancock said.
''But I'm just glad to see so many people voting," Mr. Fey said.
Mr. Fey and Ms. Holmes said they saw many first-time voters at the polls Tuesday .
"It's been pleasantly busy,'' Mr. Fey said. "That's not always the case, especially at primaries. Some of them have been primarily dismal.''
Today is Friday, Dec. 13, the 347th day of 2013. There are 18 days left in the year. 1863 -- 150 years ago: Merry sleigh bells jingle in our streets in the wake of a driving northwest storm of snow and rain. 1888 -- 125 years ago: Thomas Campbell was elected commander of John Buford Post 243, Grand Army of the Republic. 1913 -- 100 years ago: Thomas B. Reidy was named consul of C.W. Hawes Camp No. 1550, and L.H. Eihl was named consul of Camp 29, Modern Woodmen of America. 1938 -- 75 years ago: Rock Island aldermen last night upheld the view of a petition signed by 150 businessmen that the city should not install parking meters. 1963 -- 50 years ago: Total volume during the Christmas mailing season may reach 12 million pieces in Rock Island, according to Rock Island Postmaster Carl J.L. Wessel. 1988 -- 25 years ago: The aromas filling the air at the Rock Island Lines depot in Rock Island soon will be prime rib and roast duck rather than sawdust and plaster. A tourist train will be offering dinner excursions in mid-February or early March, according to Dan Carmody, executive director of the Development Association of Rock Island.