The Republican Party is trying to reclaim some of its old turf in California on Tuesday, after losing a string of U.S. House seats in 2018 that helped Democrats reclaim control of the chamber.

A Republican takeover of the House appears highly unlikely, however, and the fate of GOP candidates in toss-up districts in Orange County, the Central Valley and the Los Angeles area could turn on whether voter disdain for President Donald Trump trickles down the ballot in the heavily Democratic state.

Two years ago, Democrats pulled off a string of upsets as suburban voters nationally recoiled from the Trump agenda, grabbing seven GOP-held districts, including four all or partly in the one-time Republican stronghold of Orange County.

Those losses were humiliations for the state GOP, which has seen its standing with voters steadily erode over a generation. Republican presidential candidates carried California in nine of 10 presidential elections from 1952 to 1988.

But California has become increasingly Democratic with its diversifying population: Republicans hold only seven of the state’s 53 House seats, the party hasn’t won a statewide race since 2006 and registered Democrats outnumber GOP voters by nearly 2 to 1.

Republicans hoping for a rebound have argued that incumbent Democrats lack independence and are tied too closely to House Speaker Nancy Pelosi, while Democrats have depicted Republican candidates as subservient to Trump, who is widely unpopular in California outside his loyal base.

The key contests:

A BATTLEGROUND AT THE EDGE OF LOS ANGELES

Democrat Katie Hill captured the swing 25th District in a 2018 upset, seizing the last Republican-held House seat anchored in Los Angeles County. She was gone in less than a year, resigning amid a House ethics probe involving sexual misconduct.

The seat is now held by Republican Rep. Mike Garcia, a former fighter pilot and defense industry executive who won a May special election to fill the vacancy. He’s in a rematch with the state lawmaker he defeated last spring, Christy Smith.

The district, which includes a slice of Ventura County that is home to the Ronald Reagan Presidential Library, has a Democratic registration edge.

THE COMEBACK KID?

Former Republican Rep. Darrell Issa was a national figure as chairman of the House Oversight and Government Reform Committee from 2011 to January 2015, emerging as a chief antagonist of President Barack Obama.

But his once-conservative district straddling San Diego and Orange counties gradually changed, like much of California, and he decided not to run for reelection two years ago after nearly losing the seat in 2016.

Now, he’s back as a candidate in the neighboring 50th District, which was held by Republican Rep. Duncan Hunter until he resigned earlier this year after pleading guilty to a corruption charge. Issa, a car alarm magnate who at one time was the wealthiest member of Congress, is matched against 31-year-old Democrat Ammar Campa-Najjar, who nearly ousted Hunter in 2018 despite the district’s conservative tilt.

Issa is closely aligned with Trump and could suffer if the president does not deliver a strong showing in the district that the president carried by 15 points in 2016.

FIGHT IN FARM COUNTRY

In one of several rematches on the ballot, former U.S. Rep. David Valadao is trying to win back the seat he lost two years ago to Democrat TJ Cox by 862 votes. It’s expected to be close again.

The Central Valley district has a wide Democratic registration edge but has shown a willingness to embrace Republican candidates before. Valadao endorsed Trump this time after withholding his support in 2016 — a risk in a district the president lost by 15 points.

But he also stressed an independent streak and an ability to work across the political divide.

Cox has been campaigning on health care and immigration reform in a district with a large Latino population. Both candidates have seen unfavorable publicity tied to their business interests.

GOP AIMS TO RETAKE LONGTIME REPUBLICAN DISTRICT

Former Republican Rep. Dana Rohrabacher served for decades before losing in 2018 to Democrat Harley Rouda in the coastal 48th District in Orange County, once a conservative bastion. The loss carried symbolic weight in a county known as a foundation block in the Reagan revolution.

This year, Rouda is defending his seat against Republican Michelle Steel, who heads the county Board of Supervisors.

The district has a GOP registration edge, but Democrats have been closing in. Hillary Clinton carried the county by nearly 9 points in 2016. Taxes and health care have been prominent issues.

A REMATCH IN ORANGE COUNTY

Another longtime Republican seat anchored in Orange County fell to Democrat Gil Cisneros in 2018. Republican Young Kim, a former state lawmaker who was born in South Korea and grew up in Guam, is back for a second try in the 39th District.

The district has grown more Democratic over two years, and the party has opened up a slight registration advantage.

Kim has argued that Cisneros didn’t live up to his promise to be an independent voice in Washington, instead falling in line with Pelosi.

Cisneros, a Navy veteran and $266 million lottery jackpot winner who founded a charitable foundation with his wife, has depicted Kim as a lockstep supporter of Trump.

DEMOCRAT LOOKS FOR A REPEAT

The Central Valley’s 10th District has a Democratic tilt, but the agriculture-rich area also has a history of sending Republicans to Congress.

Not surprisingly, first-term Democratic Rep. Josh Harder has been touting a willingness to work across the party divide, along with highlighting his work to secure funds for water projects, a priority in the region.

Republican Ted Howze, a veterinarian, lost the backing of national Republicans earlier this year over derogatory online posts about Muslims and Hillary Clinton that the candidate said he did not write. He’s depicting himself as an outsider running against the Democratic establishment and has echoed Trump’s criticism of efforts to defund police departments.

Harder, a venture capitalist, had a nearly $4 million cash advantage in mid-October, which could prove decisive.