Presidential hopeful Bernie Sanders is making a major campaign push in California in hopes of gaining ground on Democratic nomination frontrunner Hillary Clinton, but faces an 18-percentage-point gap among the state’s voters likely to participate in the Democratic primary, according to an ABC7-Southern California News Group poll released Monday.

Vermont Sen. Sanders, who on Saturday started a series of eight Southern California rallies over four-day period, is favored by 39 percent of likely Democratic primary voters, while former Secretary of State Clinton is preferred by 57 percent. The numbers are virtually identical to a poll by the same group released three weeks ago.

“Pollsters have been wrong about Sanders before, especially in Michigan, but we see little in our research to indicate that Sanders will overtake Clinton in California,” said Jay Leve of SurveyUSA, which conducted the poll. “Nor is there a trend line that suggests that Sanders would catch Clinton in California if only he had more time.”

The latest poll numbers are virtually identical to a SurveyUSA poll three weeks ago. The survey in the Clinton-Sanders matchup polled 803 likely Democratic primary voters, with a margin of error of 3.5 percent.

Sanders told The Orange County Register on Sunday that strong showings in the remaining nine primaries and caucuses are essential to any chance at the nomination. California has 475 pledged delegates, the most of any state, and is particularly important, he said.

But with Election Day two weeks away and mail balloting already underway, Sanders faces a steep road. The poll released today was conducted Thursday through Sunday.

Sanders has a 5-percentage point lead among voters 18-34, but trails among all other age groups, all ethnic groups and among both men and women. RealClearPolitics.com’s aggregation of four April polls showed Sanders trailing by a less – but still significant — 10-percentage points.

While Clinton’s current delegate count makes it nearly impossible mathematically for Sanders to catch up, he is hoping a strong showing in the remaining races will help him persuade super delegates to shift allegiances. Super delegates, who account for about 15 percent of all delegates, have mostly lined up behind Clinton. But unlike pledged delegates can change who they support.

In the race to replace outgoing U.S. Sen. Barbara Boxer, two Democrats — California Attorney General Kamala Harris and Rep. Loretta Sanchez, D-Orange — continue to lead the field. The primary allows voters to cast ballots for any candidate regardless of party affiliation, and the top two vote-getters advance even if they belong to the same party.

Harris polled at 31 percent and Sanchez at 22 percent, similar to the last SurveyUSA poll and to other statewide surveys. Former state Republican Party Chairmen Tom Del Beccaro and Duf Sundheim were tied with 9 percent and GOP activist Ron Unz came in at 7 percent.

As with nationwide polls, there is a strong dislike in California for both parties presidential frontrunners. Among all state voters polled, 48 percent had an “extremely negative” view of presumed GOP nominee Trump and 30 percent had an “extremely negative” view of Clinton. Just 13 percent had that view of Sanders.