Boulder City, Nevada (CNN) Republican Sen. Dean Heller is handing out the styrofoam plates and cracks an occasional joke at the annual Fourth of July pancake breakfast here when a man looks up from the line and asks unprompted, "Are you supporting our President? If you are, I'm voting for you."

For Republican voters in Nevada, Heller's loyalty to Donald Trump is one of the central questions of the race. As the most vulnerable Republican senator running for re-election this year, Heller has had to walk a fine line between supporting the President enough to appease his base while also avoiding taking positions that could put into further jeopardy his re-election bid in a state Hillary Clinton won in 2016 by just two percentage points.

"I would like the party to work together," said Carol Navarra, a 72-year-old Boulder City resident and a Republican. "Trump's the President, and I grew up when you respected the President no matter what."

Challenging Heller is Rep. Jacky Rosen, a relative newcomer to politics elected to the House in 2016 in a district Trump narrowly won. Before that she worked as a computer programmer and as a former president of her synagogue.

One particular issue that voters brought up to CNN in interviews over the July 4th holiday was immigration. Trump has made the issue central to the midterm elections, and during his visit to Nevada last week, he campaigned on his border wall, his crusade against sanctuary cities and his tough talk on MS-13. Trump went after Rosen during the visit, calling her "Wacky Jacky" and saying a vote for Rosen is a vote for a weak border and crime.

"We got to get immigration under control. They have to pass a good immigration law" said Jim Villella, a Heller supporter. "People are coming over the border outside of the checkpoints and assuming they can come right in, cut the line in front of people who have been waiting for years."

His wife Theresa adds "I just think everyone has the right to relocate here, but let's do it the legal way."

Rami Hernandez, a 27-year-old immigrant and new US citizen, will vote for the first time in the midterm elections. Sitting at the Boulder City parade with his family, Hernandez says he will likely back Rosen because he says Heller is too close to Trump.

"The whole situation on the border just brought more of a spotlight to immigration," Hernandez said. "I feel like it's my duty to represent the people who don't have that voice. When I became a citizen, that was the first thing I thought about. I was like 'I'm going to represent the people that I know who can't have this voice.'"

Heller is striking a balance between his past moderate record on immigration reform and his new reality: he can't abandon Trump and guarantee a win in Nevada.

Heller came out against the administration's policy of separating families on the border in June, sending a letter along with a dozen other GOP senators calling for the practice to be paused while Congress negotiated a solution.

"I think the President made the right step in trying to keep these families together, he reversed his initial position on this, but I do think it's going to take legislation," Heller said. "We'll push for some legislation to make it permanent."

In February, when Heller was staring down a primary challenger, the senator voted for the Trump administration's immigration bill and against a narrow, bipartisan compromise bill that would have provided a path to citizenship for recipients of DACA, but not their parents. as well as allocated $25 billion for border security including Trump's wall.

Democrats have argued Heller flip-flopped as they contrast his February votes with his vote in 2013 to support another bipartisan immigration bill that would have overhauled the country's legal immigration system, provided a path to citizenship for millions and aggressively expanded the use of border patrol agents and technology along the Southern border.

Heller argues there's nothing inconsistent about his vote, but that he wasn't going to back a bill that the Trump administration whipped against and adamantly opposed.

"I don't want an exercise in futility. That was a bill that the President wouldn't sign. I want to get something done," Heller said. "When Obama was President, he had his support of a particular piece of legislation and I figured we'd get something done. That's why I supported the immigration bill five or six years ago...Just to vote on legislation that we know won't pass the President's desk or he won't sign, is I don't think the right message."

For her part, Rosen has tried to tie Heller to Trump's immigration position on the trail. She argues not only is the state the home of many DACA recipients and a growing immigrant population, but that the Trump administration's decision to end Temporary Protected Status for immigrants from Honduras, Haiti and El Salvador could have extreme ramifications for Nevada's restaurant and hospitality industry that employs thousands of workers with TPS status.

On Thursday, Rosen released a Spanish-language television ad about a recent trip she took to the border where she visited facilities and toured a tent encampment in Tornillo, Texas, where unaccompanied minors are held. The ad features audio from ProPublica of children in holding facilities crying for their parents.

"This is a 'where were you' moment," the ad's narrator says in Spanish in the ad.

Rosen doesn't have the kind of long-term record Heller has on immigration and is also facing the pressure from the base of her party on immigration.

In an interview with CNN, Rosen said she doesn't agree with some of her more liberal Democratic colleagues who have called to abolish Immigration and Customs Enforcement in recent weeks.

"ICE does a lot of other things that people don't realize. They work on counterterrorism, cyber security. I'm a former computer programmer who worked in tech. Counterterrorism, cyberterrorism, it's real," Rosen said. "ICE has other jobs so what we need to do is we need to ask the President to stop his reckless and harmful policies right now."

Rosen says she opposed to Trump's border wall.

"I think the idea of a physical wall, I think President Trump has the wrong idea for that," Rosen said. "I'm a woman in technology, I think that we have to consider our border and use the technology we have to be sure that we secure it. If you build a six foot wall, somebody may jump eight feet. But, maybe there's surveillance...there's many high tech things that we can use to be sure we are protecting our borders."

Unlike the Democrats who are running in red states where Trump won decisively in 2016, Rosen has cut a more progressive profile. Rosen joined the rest of her caucus last week and voted against a Republican-negotiated immigration bill in the House of Representatives that would have provided a path to citizenship for DACA recipients in exchange for full scale changes to the legal immigration system and $25 billion in border security.

"It built a wall. It hurt immigrants. It's going to limit the number of immigrants, it's going to cancel the diversity visa lottery. There are so many things in there that just aren't smart," Rosen said.