Democrats are renewing their efforts to eradicate all California Republicans from Congress, targeting two more GOP representatives for 2020.

Reps. Devin Nunes of Tulare and Duncan Hunter of Alpine (San Diego County) are on the way-too-early list of 33 Republican House members that the Democratic Congressional Campaign Committee is looking to unseat.

Last year, when Republicans lost seven California seats and 40 across the nation, “was just the tip of the iceberg for Democrats,” Illinois Rep. Cheri Bustos, chair of the Democratic committee, said in a memo released Monday. “By putting our plans in motion earlier in the cycle than ever before, we are demonstrating to Democrats across the country that the political arm of House Democrats is operating in high gear from the start.”

The committee’s announcement at this point does little more than point out vulnerable Republicans. But as the election gets closer, Democratic challengers in those districts could get money from both the party and independent groups that lean their way.

There are plenty of reasons for California Democrats to feel confident. The 65 percent turnout in November was the highest for a midterm since 1982, and that number is likely to grow significantly for the 2020 presidential election.

In deep-blue California, more voters means more Democrats, said Paul Mitchell, vice president of the nonpartisan Political Data Inc., which collects information on voting behavior for political groups across the state.

The 2018 midterm “was obviously a wave (for Democrats), but it might have been a precursor of a bigger 2020 wave and not an aberration,” Mitchell said. “They still have room to grow.”

Then there’s the Trump factor. Presidential elections typically bring out more voters than midterm contests, and with President Trump on the top of the ballot, that’s not likely to be good news for the GOP in California.

A December poll by the Public Policy Institute of California found that 61 percent of likely voters, including 83 percent of Democrats and 67 percent of independent voters, disapproved of the job Trump was doing as president.

“Polling during the last election cycle showed a big reason for the high turnout was Trump,” Mitchell said. And even without Trump’s name on the ticket, unhappiness with the president was a major factor in GOP losses throughout the state.

With Trump in full cry on the campaign trail, Republican candidates in California will find themselves hard-pressed to ignore the president and his policies, even if they are unpopular in the state.

And for candidates like Nunes, who has tied himself tightly to the president, their fate could depend on Trump.

But in California, Democrats could be a victim of their own success. With an overwhelming 46-7 margin in the state’s congressional delegation, Democrats have grabbed not only the low-hanging fruit, but also everything but that at the tip-top of the political tree.

Nunes and Hunter faced the toughest challenges in 2018, which is why they made the Democratic target list. But they both still won.

Despite massive spending by Democrats, Nunes beat Democrat Andrew Janz, 53 percent to 47 percent, in his Central Valley district, where Republicans have a 40 percent to 32 percent registration advantage.

In Southern California, Hunter barely squeezed by little-known Democrat Ammar Campa-Najjar, who already has announced he’ll seek a rematch in 2020. But there’s no guarantee Hunter will be the opponent.

Hunter, who along with his wife is facing trial on federal charges relating to misuse of campaign funds, is a GOP target as well. Matt Rahn, the mayor of Temecula (Riverside County), already has announced that he’ll challenge Hunter. The list of Republican contenders will probably grow.

The five other Republican House members in California easily won re-election in strong GOP districts and are well-positioned to withstand another Democrat onslaught next year.

That won’t keep Democrats from trying, however, even as they also work to defend longtime GOP seats they won in November.

“As the saying goes, the best defense is a good offense,” Bustos said in her memo.

John Wildermuth is a San Francisco Chronicle staff writer. Email: jwildermuth@sfchronicle.com Twitter: @jfwildermuth