Washington — In a cycle that appears to be exceedingly favorable for Republicans hoping to take control of the Senate, one seat representing a Republican stronghold is facing a surprising challenge this November.

Independent Dan Osborn is running an unexpectedly competitive Senate race in deep-red Nebraska in his bid to unseat two-term Sen. Deb Fischer in a race that could shake up the fight for control of Congress' upper chamber.

Osborn, a Navy veteran, mechanic and union leader, has been garnering millions of dollars in outside support and prompting Republicans to redouble their efforts in a race that was thought to be an easy win.

Polling, albeit limited, indicates a tight race between Fischer and Osborn. A series of recent statewide polls suggest the race is within single digits, including an Independent Center poll released last week that showed Osborn up 47% to Fischer's 42% in a survey of likely voters in the state. An Osborn-commissioned SurveyUSA poll conducted last month found the independent up 45% to Fischer's 44%. And in Nebraska's second congressional district, which is home to Omaha and is the most evenly divided district in the state, a New York Times/Siena poll released late last month showed Osborn leading Fischer by 11 points. There is no Democrat in the race. The surveys suggest the Nebraska Senate race is among the closest in the country, according to 538's polling averages.

Republicans have a favorable Senate map this year, with pickup opportunities across a number of states and few seats to defend. And although Nebraska is considered more friendly to Republicans than the two states — Texas and Florida — that Democrats have eyed, Osborn's challenge appears to be a formidable one in the unusual race.

"It's more competitive than it should be," Randall Adkins, a professor of political science at the University of Nebraska-Omaha, said of the Nebraska Senate race.

Osborn led the strike at Omaha's Kellogg plant in 2021, gaining some national attention in the process. But the 49-year-old is a political newcomer. And he's leaned into a populist message to pledge to lead the state as an independent who will work for Nebraskans, while painting his opponent as an establishment politician controlled by corporate interests.

The independent candidate touted the polls in a statement to CBS News, saying they "match up with what I'm seeing across Nebraska."

"Our message of standing up for small businesses, family farmers, and working families is resonating because Nebraskans want a senator who listens to them, who shows up for them and who will be a strong voice for them in the Senate," Osborn said.

Osborn's opponent, Fischer, has been in the Senate for more than a decade and serves on the powerful armed services and appropriations committees. The 73-year-old two-term incumbent who's a reliable GOP vote in the Senate has won relatively easily in the red state and hasn't had a problem raising money, so her race wasn't expected to be a competitive one. Adkins thinks Fischer may have taken her reelection campaign for granted.

"I don't think that the Fisher campaign realized how competitive this race was going to be," Adkins said, adding that it was "radio silence" from the incumbent all summer, while Osborn was operating "under the radar."

"He was just sort of keeping quiet," Adkins said of Osborne. "And we get to September, and it's within the margin of error."

The campaign has ramped up in recent weeks. Fischer, a cattle rancher, has touted an endorsement from former President Donald Trump, along with a new advertisement focused on her backing from former Rep. Tom Osborne, long-time coach of the Nebraska Cornhuskers. Osborne clarifies in the advertisement that he doesn't know the independent candidate of a similar name.

Meanwhile, the National Republican Senatorial Committee has placed $522,000 in advertisement spending and reservations in the race, according to AdImpact.

The spending comes as Osborn has seen a flood of investments to his campaign. Overall, outside spending supporting the independent has climbed to $4 million, according to OpenSecrets. Much of that comes from the Retire Career Politicians PAC, which receives substantial donations from a left-leaning dark money group known as the Sixteen Thirty Fund.

The investments underscore that the race could be within striking distance for Osborn.

Meanwhile, Fischer and Republican allies have derided the independent as a "Democrat in disguise."

"Dan Osborn claims to be an independent, but he's funded by the same billionaire Democrats supporting Kamala Harris, supports mass amnesty and social security for illegal immigrants, and was caught on tape saying he loves Bernie Sanders," the Fischer campaign said in a statement to CBS News. "When Nebraskans learn that Dan Osborn is a liberal Democrat in disguise, they won't stand for it."

Osborn has pledged not to caucus for either party if he's elected to the Senate, where four independents currently caucus with Democrats. And shortly after the primary, he said he wouldn't accept endorsements from any side of the political spectrum.

"People are coming out of the woodwork now," he told reporters in May. "I want to be clear that I'm an independent. I want to stay true to who I am, and that is an independent. I can't be charmed, I can't be schmoozed, I won't suck up to anyone, and most importantly — I cannot be bought."

On the issues, the independent has expressed positions generally shared by moderates — like opposition to national abortion restrictions, along with support for "reasonable gun safety measures" and stronger border security.

Nebraska has nearly twice as many registered Republicans as Democrats, making Democrats' bids in the state often fruitless. Indeed, a Democrat hasn't held statewide office in Nebraska since 2012. And Trump won Nebraska by nearly 20 points in 2020.

But Nebraska is also home to nearly as many nonpartisan voters as Democrats, meaning the two groups could feasibly come together to rival the number of registered Republicans in the state to elect a candidate, despite the state's leanings.

Still, previous Senate bids from independent candidates in red states under similar conditions have ultimately fallen short, like in Utah in 2022 and Alaska in 2020. The Cook Political Report, which shifted the race's rating late last month from solid to likely Republican, cited the outcomes in an analysis, while noting that Osborn's background differs from the other independent candidates.

Adkins said something is being "tested here that we haven't seen in Nebraska before," where the minority party doesn't field a candidate when a moderate or independent candidate is running, bucking the typical dynamic where the race is all-but decided after the Republican primary.

"This campaign just got started," he said.