Two of California's best-known Democrats are slipping in the polls as the calendar advances closer to Election Day.

In fact, both Lt. Gov. Gavin Newsom and U.S. Sen. Dianne Feinstein have only single-digit leads over their opponents, the results show.

In the race for governor, a Probolsky Research poll, conducted between Aug. 29-Sept. 2, shows Newsom leading Republican businessman John Cox by a mere 5 points, with 17 percent of respondents undecided, the San Francisco Chronicle reported.

Feinstein faces similar problems, with the poll showing her with only an 8-point advantage over progressive challenger Kevin de León. A quarter of the respondents told the pollsters they remain undecided.

Both Cox and de León have cut their opponents' leads since the primaries in June. Newsom took 34 percent of the vote while Cox received 25 percent. In California's "jungle primary" system, the two top finishers face off in the general election, regardless of party.

In the U.S. Senate race, Feinstein received support from 44 percent of voters while de León received only 12 percent -- though other candidates ran as well.

The Hispanic vote has been a source of frustration for Newsom, who has basically split that constituency with Cox, despite Hispanics historically preferring Democrats, the Chronicle reported.

For Feinstein, one worry is support among the Republicans, who have no candidate of the Senate race. De León, despite positioning himself as a more progressive candidate than Feinstein, has 5-point lead among Republicans. Still, nearly half of Republicans in the poll said they are undecided.

De León has been relentlessly attacking Feinstein from the left for not being progressive enough. Amid the chaotic Supreme Court nominee Brett Kavanaugh confirmation hearings, the progressive Democrat attacked Feinstein for adhering to the process rather than joining the protesters.

“We should be praising the protesters and standing outside with them, not apologizing for their actions,” he tweeted. “We need a senator from California who will stand up and #RESIST not #ASSIST.”

The attack from de León followed Feinstein's apology Wednesday after a protest broke out during the Kavanaugh hearing.

“I'm sorry for the circumstances,” the senator told Kavanaugh. “We'll get through it.”

Cox, meanwhile, has been campaigning on the ground and went to the state’s multiple Division of Motor Vehicle offices with a promise that “help is on the way” to those waiting in lines.

“This is a great reference point for everything John talks about,” campaign spokesman Matt Shupe told the Chronicle. “It's about bringing more transparency to government. It's about approaching issues like a businessman. It's about reforming a government entity that nobody is happy with.”