Chairman Ed Royce, R-Calif., arrives for a House Foreign Affairs Committee hearing last November. Bill Clark | CQ Roll Call | Getty Images

A fresh poll in a closely watched congressional race in Southern California shows Republican Young Kim with a slight lead despite having been outspent by nearly 5 to 1 by her challenger, Democrat Gil Cisneros. A former state lawmaker, Kim is competing against Navy veteran and philanthropist Cisneros to fill the seat being vacated by retiring Rep. Ed Royce, a 13-term Republican from California's 39th Congressional District. Prior to serving one term in the state Assembly, Kim worked as a staffer for Royce, who is chairman of the House Foreign Affairs Committee. Royce has endorsed Kim as his successor.

Most of the district is in northern Orange County, which historically has been a GOP stronghold, but it includes eastern Los Angeles County and southwestern San Bernardino County. Immigration is one of the hot-button issues in the district, which has a high Asian and Latino population.

Kim leads in poll

A Monmouth University Poll of potential voters conducted Sept. 13-16 and released this week shows Kim is leading, 46 percent to 42 percent, among all potential voters, or those voters who have participated in an election since 2010 or are newly registered to vote. Twelve percent are undecided. The 4-point spread was within the 6.9-point margin of error in the random telephone poll of 402 potential voters.

Young Kim, Republican U.S. Representative candidate from California, waves during a Fourth of July parade in Hacienda Heights, California, on Wednesday, July 4, 2018. Patrick T. Fallon | Bloomberg | Getty Images

"One thing I notice that's different in this race than in other races is that the Democratic candidate is significantly more negative (in terms of a favorability rating) than in other districts that we've polled," said Patrick Murray, director of the independent Monmouth University Polling Institute. According to the university's poll, Kim is "better liked than Cisneros." It said Cisneros has a 23 percent favorable rating and 24 percent unfavorable, while Kim has a 32 percent favorable rating and 11 percent unfavorable. The demographics in the mostly working-class district have been changing and Democrats believe they have a good chance to flip the House seat. More than 65 percent of the residents are people of color, with Latino and Asians making up the largest groups. Democrat Hillary Clinton carried the district in 2016 by about 9 points, although registered Republicans still outnumber Democrats in the Orange County portion of the district.

'All politics isn't local'

"The overriding issue in these races is Trump, and sometimes all politics isn't local," said Fred Smoller, a political science professor at Chapman University in Southern California. Smoller believes the immigration issue should help pull in votes for Cisneros, but he said the Asian community tends to vote "very strongly Republican on the issue on immigration" so that could ultimately boost numbers for Kim. Kim, who emigrated from South Korea as a child and describes herself as a small business owner, has been supportive of President Donald Trump's call to beef up border security as a condition for comprehensive immigration reform and sided with the president in opposing California's so-called sanctuary state laws. Kim declined a CNBC interview request to comment on key issues.

Cisneros, a multimillionaire who won a $266 million lottery jackpot in 2010 after getting laid off from Frito-Lay, has been vastly outspending his Republican challenger and money raised includes a $4.5 million loan from the candidate himself. The money Kim received included donations from several prominent corporate PACs, including Koch Industries and Exxon Mobil.

Cisneros critical of Trump

Cisneros, who has been active in philanthropic causes in the Latino community, has been critical of Trump's immigration policies and separation of families at the Mexico border.

Gil Cisneros, Democrat running for California's 39th Congressional district seat in Congress, speaks to the Hacienda Heights Improvement Association meeting at the Hacienda La Puente Unified School District board room in the City of Industry, Calif., on Monday, May 21, 2018. Bill Clark | CQ Roll Call | Getty Images

He said in a recent interview with CNBC that Kim would be "nothing more than a rubber stamp of the Republican agenda and not hold the president accountable." In contrast, Kim's advertisements have messaged that she's "independent" and "bipartisan." Her campaign was asked to comment on the new poll and repeated those same points in an email response. "The poll reflects Young Kim's proven independent record achieving bipartisan results to protect domestic violence victims, homeless children and veterans — and helping local small businesses grow and add jobs," said Patrick Mocete, a Kim campaign spokesman.

Contest seen as 'toss-up'

With less than 50 days before the Nov. 6 election, Sabato's Crystal Ball at the University of Virginia and the Cook Political Report — two nonpartisan trackers of House races around the nation — list the 39th District as a "toss up." Orange County Republican Party Chairman Fred Whitaker said he's "heartened" by the Monmouth poll results that show a slight lead for Kim, pointing out that Royce won re-election in the 2016 by a 14-point margin "even in a very challenging cycle for Republicans." Whitaker also called Kim "an excellent candidate that meets the demographics of the district. She's an excellent messenger for our message. And we've been working extraordinarily hard in that seat for really even a year — even before Congressman Royce decided to retire. We knew the Democrats were going to come after all these districts."

GOP attack ads

Cisneros has been dogged by sexual harassment allegations and has been the subject of attack ads by the Congressional Leadership Fund, a Republican super PAC that has also targeted other Democrats in tight races. One of the PAC's ads repeated the misconduct allegation against Cisneros. Melissa Fazli, a fellow Democrat who lost a California state Assembly race in the June primary, accused Cisneros of asking her for sex in exchange for a campaign donation. Fazli alleged in a press release posted on Twitter in May that the "inappropriate encounter" stems from a conversation she had with Cisneros in front of elevators at a hotel in San Diego during the California Democratic Party Convention. Cisneros denied the claims when they were first reported. Moreover, campaign spokesperson Daphne Sigala last month called out the use of "special interest and dark money connections to politicize a patently false allegation." Nic Jordan, another Cisneros campaign official, downplayed the Monmouth poll and cited its "small sample size" and added "our own polling finds Gil doing better with voters most engaged and interested in the election." The Monmouth poll released Tuesday found 47 percent of the district voters approve of the job Trump is doing while the same percent also disapprove. The Cisneros campaign official calls that finding a sign the New Jersey university's poll is "a real outlier." An internal poll released last month by the Cisneros campaign of 600 likely voters showed the Democrat ahead by 11 percentage points. The poll was conducted Aug. 1-6 by San Francisco-based Tulchin Research and also showed 57 percent of the voters had an unfavorable view of Trump and 41 percent a favorable view.

Cisneros said his campaign has attracted not only Democrats but some Republicans and independents "that say it's time for a change. We need people in Washington that are going to hold the president accountable. But we also need individuals that have a commitment to the country that are willing to get the government working for people again." Cisneros and his wife, Jackie, a former producer at KNBC in Los Angeles, used a portion of their 2010 winnings from the California Mega Millions lottery to start a foundation to help kids go to college. KNBC and CNBC are owned by NBC Universal, a unit of Comcast Corp.

'Best chance' for Democrats