Democratic presidential nominee former Secretary of State Hillary Clinton (R) and Republican presidential nominee Donald Trump speak during the town hall debate at Washington University on October 9, 2016 in St Louis, Missouri. (Chip Somodevilla/Getty Images)

SAN FRANCISCO (CBS SF) – Three weeks before Election Day, a new KPIX 5 / SurveyUSA poll finds Democratic presidential nominee Hillary Clinton continuing to have a double-digit lead over Donald Trump in California.

Meanwhile, support for the Republican presidential nominee has dropped to levels not seen in the state in decades.

Survey USA polled 725 likely California voters and those who voted early, after the second debate last week. Among those polled, Clinton is leading Trump, 56 percent to 30 percent.

• Download full KPIX 5 / Survey USA poll results (.pdf)

Compared to a poll taken after the first debate, support for Clinton and Trump has dropped by 3 points apiece, while the number of undecided voters has increased to 7 percent.

If the result holds, Trump’s 30 percent support would be the lowest percentage for a GOP presidential candidate in California in the past 100 years. The Republican currently holding the record is former President George H.W. Bush, who received 33 percent of the vote during a three-way contest against Bill Clinton and Ross Perot in 1992.

In the past month, SurveyUSA found Trump’s support eroding among younger voters (29 percent in mid-September to 20 percent now), independents (28 percent to 17 percent) and even among California gun owners (47 percent to 37 percent.)

Despite recent news of Trump’s alleged sexual misconduct, the Republican nominee has increased support among Evangelicals in the past month (46 percent in mid-September to 53 percent now.)

Among third party candidates, Libertarian Party candidate Gary Johnson has 4 percent support and Green Party candidate Dr. Jill Stein has 2 percent.

The poll has a margin of error of plus or minus 3.7 percent.