Immigration and border security issues unify Republican voters while dividing Democratic voters in California, a statewide poll has found.

The findings of the new UC Berkeley Institute of Governmental Studies poll, co-sponsored by the Los Angeles Times, illustrate some of the political difficulties President Biden faces in dealing with the large number of unauthorized migrants crossing the U.S. southern border.

Even in California, a Democratic stronghold, registered voters by 62% to 30% say U.S. borders are not secure in preventing people from entering the country illegally, the poll found. The majority who say the border is not secure is even larger among likely voters.

Voters who support former President Trump, are conservative or identify as Republicans are nearly unanimous in saying the border is not secure. Among strongly conservative voters, 88% say the border is not secure, versus 8% who say it is.

Democrats, liberals and voters who support Biden are more evenly divided. Among California voters who identify as strongly liberal, 54% say the border is secure; 30% say it is not.

Democrats also split on the question of whether unauthorized immigrants create a burden for the country. Overall, 42% of registered voters say migrants are a “major burden,” 30% say they are a “minor burden,” and 22% say they are not a burden, the poll found.

“The findings show that immigration is not clear-cut even in California, whose reputation as a sanctuary state often colors discussion on the issue,” said G. Cristina Mora, co-director of the Institute of Governmental Studies.

The divide among Democrats could signal trouble for Biden on the 2024 campaign trail, although more so in other states than in California, said Mark DiCamillo, director of the poll. “The odds of a [Republican] carrying the state are very long,” he said.

In California, the effect is more likely to play out in competitive congressional elections, which could help determine the House majority. Those include the race to fill the seat of Rep. Katie Porter (D-Irvine), who is running for U.S. Senate, as well as competitive districts in northern Los Angeles County and the Central Valley. Republican candidates in those districts could center immigration issues as part of their platforms, DiCamillo said.

“This issue is one that could play to the Republicans’ favor,” he noted.

As the number of unauthorized immigrants crossing the border has increased, Biden has come under fire from Republicans, who cast his border policies as weak, but also from some fellow Democrats.

Democratic mayors of New York and Chicago, among other large cities, have said services are buckling under a steady swell of migrants and have criticized the federal government for its handling of the issue.

In Congress, Republicans have been insisting that Biden agree to major changes in immigration policy, especially regarding the legal right of migrants to claim asylum in the U.S. In the Senate, Republicans have insisted on a border agreement as their price for voting in favor of sending additional aid to Ukraine, a high priority for Biden.

Unauthorized migration across the U.S. southern border hit record levels in fiscal 2023, which ended in September, topping 2 million for the second year in a row.

Many of the migrants who arrive at the southern border seek asylum, claiming persecution in their home countries. But the issue does not end at the border: The thousands of daily arrivals have overwhelmed an aging immigration system and created a backlog of asylum cases. Asylum seekers who are released into the U.S. and are given a court date are waiting years, if not a decade, to appear before a judge.

Biden has indicated a willingness to accept at least some of the Republican demands, which has angered some Democrats and immigration advocates.

Reaching an agreement remains an uphill battle, however, and the poll demonstrates how the issue consolidates the Republican voting bloc while dividing Democrats.

Voters are split over their view of the nation’s asylum laws, the poll found. Republican voters, conservatives and voters who support Trump agree that the laws are too lenient.

Democrats, meanwhile, are split: 17% say the law is too lenient, 29% say it’s about right, and 33% say it’s too restrictive. However, among those who identify as strongly liberal, a majority, 56%, say the law is too restrictive, and 6% call it too lenient, while 24% say it is about right.

Views of the asylum laws do not vary much across lines of race or ethnicity, the poll found.

The poll also found widespread skepticism that new laws would be effective in reducing the number of migrants arriving at the border: 45% of voters think new laws would be effective; 42% say they would not. Liberal voters are much more likely than conservatives to say that new laws would not be effective.

Immigrants are more likely than native-born voters to say that new laws would have an impact: 53% of California voters who were born in another country say they would be effective, while 32% say they would not. Native-born voters are evenly divided on that question.

The Berkeley IGS poll was conducted online Jan. 4-8 among a random sample of 8,199 registered California voters, including a weighted sub-sample of 4,470 voters likely to take part in the March 5 primary.

The results were weighted to match census and voter registration benchmarks, so estimates of the margin of error may be imprecise. The results have an estimated margin of error of 1.5 percentage points in either direction for the full sample.