Republicans’ dreams of winning retiring Sen. Harry Reid Harry Mason ReidThe Supreme Court vacancy — yet another congressional food fight Trump seeks to turn around campaign with Supreme Court fight On The Trail: Battle over Ginsburg replacement threatens to break Senate MORE's (D-Nev.) seat are endangered.

Polls show a tight race between Republican Rep. Joe Heck and former Nevada Attorney General Catherine Cortez Masto (D) in a race that Heck had been narrowly leading for months.

The problem? Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE.

Trump's presidential campaign is faltering, and it is hurting Republicans across the country.

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But it might be hurting Heck the most. The three-term congressman withdrew his support for Trump after a 2005 video that surfaced two weeks ago showed the GOP nominee making lewd comments about kissing and groping women without their consent.

That set off a backlash against Heck from Trump supporters -- even booing him at a campaign event. The congressman privately acknowledged he’s in a “very difficult situation” for no longer supporting his party’s standard-bearer, a move that could cost him critical parts of his base.

“Nevada is really close, so anything that alienates any part of your base in a close election is not ideal, especially in such a polarized state like Nevada,” said a Republican strategist who has consulted for races in Nevada and not involved in Heck’s campaign. “I think [Heck’s] got a serious problem.”

Heck had been supportive of Trump’s candidacy, though previously criticizing the real estate mogul’s rhetoric on immigration. He told CNN last month that he trusted Trump with the nuclear codes.

The 2005 Trump tape was the breaking point for Heck and he explained at last week’s Senate debate that his “extremely personal” decision to cut ties with Trump was prompted by his work as an Army Reserve physician with domestic violence victims as well as his wife’s own experiences in a past relationship.

In audio obtained this week by CNN of a private Las Vegas fundraiser, Heck explained that he “really” wants to support Trump, but openly lamented that Trump could hurt turnout, which could in turn spill over into down-ballot races.

Democrats and Cortez Masto quickly pounced on Heck’s withdrawal of support for Trump and haven’t held back in framing his decision as a purely political move.

"Let's call this what it is — Congressman Heck is worried about his political career," she said at the debate. "Donald Trump's ship is sinking, and Congressman Heck is scurrying off it."

Nevada is Republicans’ only real pickup opportunity this cycle, after Colorado faded from the map. And both parties see their Senate majority fate running through the Silver State seat.

That’s why Heck’s decision concerns some Republicans, since he will need Trump’s base to deliver them a victory in a close race. And strategists don’t see Heck’s change of heart being the reason to sway voters who are on the fence since he has backed Trump until the last few weeks of the race.

Heck’s campaign is pushing back on the narrative, noting that he was “warmly-received” by Trump supporters at a recent event. “What we are seeing is that even those frustrated with his decision understand the importance of a Senate majority,” a campaign spokesperson told The Hill.

His Trump decision aside, political observers describe Heck, a top GOP recruit, as a strong campaigner who has kept Democrats on their toes. The race has attracted a total of more than $64 million in spending from outside groups on both sides, according to OpenSecrets.

Like all races this cycle, turnout will be key, and strategists can envision certain scenarios with Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE narrowly winning the state and Heck also pulling off a win. The latest poll has Clinton up by 7 points on Trump, yet Heck outperforming the top of the ticket. They say as the Democratic nominee inches closer to a 10-point margin, it complicates Heck’s path to victory.

“He is a fundamentally good candidate, a hard-working candidate,” said veteran Nevada journalist Jon Ralston. “He’s not a super right-wing nut that the Democrats have been portraying him as.”

The three polls conducted in the wake of the Trump tape and Heck’s withdrawal of support have showed mixed signs about the race.

A CBS/YouGov poll showed a tied race, while a CNN/ORC survey had Cortez Masto surging ahead by 7 points.

The most recent Senate survey released earlier this week by Monmouth University is a bright spot for Heck, showing him with a 3-point edge, though within the margin of error.

Monmouth University polling director Patrick Murray says his survey doesn’t show signs of loyal Trump supporters abandoning Heck. His poll found 88 percent of “firm” Trump supporters backing Heck, which is the same percentage of “firm” Clinton supporters backing Cortez Masto.

Meanwhile, Cortez Masto is hitting the campaign trail with prominent Clinton surrogates as she seeks to widen her name recognition. She’s already appeared with Sen. Bernie Sanders Bernie SandersButtigieg stands in as Pence for Harris's debate practice Bernie Sanders warns of 'nightmare scenario' if Trump refuses election results Harris joins women's voter mobilization event also featuring Pelosi, Gloria Steinem, Jane Fonda MORE (I-Vt.), and President Obama will campaign with her this weekend. Plus, she has a major boost from Reid -- who recruited her -- and his effective turnout machine. If she wins, she will likely be the first Latina elected to the Senate.

But she faces her own issues among a crucial base: Latinos. A recent poll from Latino Decisions shows Clinton leading this group over Trump, 72 to 17 percent, while Cortez Masto leads Heck among Latinos, 54 to 24 percent.

Heck is running ahead of Trump among the Latino electorate, and strategists note that he has effectively made inroads with that group especially within his southern Nevada House district.

“If [those poll numbers are] right, that’s a real danger sign for her,” Ralston said, noting that Latinos could make up 20 percent of the state’s electorate this cycle.

Political observers say that if she can gain more ground among this electorate, that would spell trouble for Heck.

“For her, it’s going to be those nonpartisan Latinos who are probably harder to mobilize,” said David Damore, a senior analyst at Latino Decisions and professor at University of Nevada, Las Vegas. “They’re obviously not necessarily attached to the parties, and that creates a little barrier in participation that she's going to need to have to overcome.”

Early voting kicks off Saturday and signals the final stretch of the race where both Heck and Cortez Masto will need to make last-ditch efforts to shore up their respective bases and sway undecided voters.

Heck’s campaign says the congressman will be campaigning in Reno and Elko over the weekend and then travel to the western part of the state in more rural areas early next week.

Cortez Masto is spending the first day of early voting at a half dozen events in Las Vegas. "We're going to spend these final days making clear to voters that she is the only candidate who will work to solve problems for them in the Senate," said spokeswoman Sarah Zukowski.