With about 43 percent of votes counted, Curtis was trailing Seegmiller by about 18 percent.
In 2006, Curtis squeaked through by just 20 votes.
"It has just been the culmination of a lot of work and a lot of volunteers. It's just overwhelming. I am almost amazed myself that it could be done," said Seegmiller, who lost to Curtis by just 20 votes in 2006. "When I first decided to run, I knew it was going to be a daunting task. That's why I committed to run at least three times. I came so close last time. It made it easier to make this last push."
Curtis raised about $500,000 and easily outspent Seegmiller in the campaign, which turned nasty in the closing days, with mailers going to voters accusing Curtis of corruption and alleging that a Seegmiller win would result in legal pot-smoking in public parks.
Mckell Ashcroft, 21, said she voted for Seegmiller. "I feel like [Curtis] didn't transcend party, and my thing is people, not parties," she said.
Curtis' re-election battle was just one of a handful of other legislators scrapping for their seats as voters went to polls with the fallout from ethics battles and a private school voucher fight still lingering in the air.
Democrats were hopeful they could pick up two Senate seats and six House seats -- including Curtis' -- whittling away at the overwhelming Republican majority in the Utah Legislature.
One lawmaker in the cross hairs is Draper Rep. Greg Hughes, who will be watching to see how much damage was done to his candidacy by allegations of ethical misconduct. The ethics committee dismissed the charges but scolded Hughes for "unbecoming" conduct. The cloud created did put him behind in his own polls, though he has fought his way back.
His opponent, Democrat Lisa Johnson, made ethics a centerpiece of her campaign. She lost to Hughes by 15 percent in 2006.
Hughes was trailing with about a third of the vote counted.
In South Jordan, Herriman and part of West Jordan, voters will decide whether to jettison Sen. Chris Buttars in favor of Democrat John Rendell. Buttars is a conservative Republican who championed moral crusades in the Legislature, but whose verbal gaffes and miscues have made him the body's most controversial figure.
Rendell held a small lead against Buttars, with 60 percent of the vote left to be counted.
It is also the first election since voters overwhelmingly rejected a controversial private school voucher law in a referendum election last November. Three House members who supported the voucher movement already have been knocked out of office, one at convention, two in Republican primary elections.
Vouchers loomed large in a Sandy Senate contest between Republican incumbent Carlene Walker and Democratic Rep. Karen Morgan. Walker is a moderate Republican who voted for vouchers, while Morgan, a teacher, made it a major issue in the campaign.