In a move that took Republican insiders by surprise, former GOP State Senator Janet Nguyen is challenging moderate GOP Assemblyman Tyler Diep for his 72nd Assembly District seat in 2020.

The looming primary battle is sparking division among party leadership, as the GOP struggles to find its footing in an increasingly Democratic region where Donald Trump’s brand of Republicanism is a tough sell.

Former Orange County GOP chair Scott Baugh prompted Nguyen to run with a Dec. 5 email to local party leaders that blasted Diep’s voting record on issues such as charter schools and his recent comments in support of organized labor, which Baugh termed “a step ladder into the penthouse of the leftist elite.”

“He brought this fight to us by campaigning as a conservative and betraying us in Sacramento,” Baugh said in a follow-up email obtained by the Register. “There is a rat in our cellar and I am turning on the light.”

But by Friday, Dec. 13, some leading Californian Republicans had jumped to Diep’s defense. California Republican Party Chairwoman Jessica Patterson, Senate Republican Leader Shannon Grove and Assembly Republican Leader Marie Waldron issued a joint statement calling Nguyen’s bid “a distraction” that “plays directly into the Democrat speaker’s playbook.”

“We call on everyone who is committed to the party to put differences aside and join us in keeping this district Republican,” the women wrote.

In an emailed response to local GOP leaders, first-term Assemblyman Diep blamed Baugh for Democrat Harley Rouda’s 2018 win in the formerly Republican-held 48th Congressional seat. The result came after Baugh challenged longtime GOP Rep. Dana Rohrabacher in the 2018 primary.

“Our Assembly Republican caucus is now down to just 18 members. We had 32 members just 12 years ago,” Diep of Westminster said. “Infighting and purity tests are not going to make us stronger.”

It’s unclear who the GOP might have to beat for the party to hold AD-72. Democrat Josh Lowenthal initially took out paperwork to challenge Diep to a rematch after losing the district seat to him by 3.2 percentage points in 2018, but he didn’t follow through. Instead, records show two other Democrats are hoping to win the seat, cancer scientist Diedre Nguyen and civil rights activist Bijan Mohseni.

The standoff between the two Vietnamese Americans in a district that includes Little Saigon was the biggest surprise to emerge in the past week as ballots take shape for Orange County’s 2020 primary contests.

A final list of candidates on the ballot March 3 for every race that touches Orange County will be set Dec. 26, when the Secretary of State releases its certified list. But local candidates had to file paperwork with the Orange County Registrar of Voters by Dec. 6, with the deadline extended until Wednesday, Dec. 11 for one county race where the incumbent decided not to run for reelection. And unless litigation or some other rare circumstance comes into play, election officials said the county’s list of candidates should stick.

Nguyen filed her paperwork on Dec. 6, a day after Baugh sent his first email about Diep.

The Fountain Valley resident has been eyeing a new position since she narrowly lost her 2018 reelection bid to Democrat Tom Umberg. She tried and failed earlier this year to win appointment to a regional water board seat. She also considered a congressional run, and she has active campaign committees for a 2020 county supervisor seat and a 2022 run for the state senate.

Nguyen has proven to be a strong fundraiser in past election cycles, spending more than $2 million in contributions during her 2018 state senate bid.

Diep raised $309,650 in the first half of the year for his 2020 election campaign, according to Secretary of State records, with $280,648 in cash at the end of the last reporting cycle June 30.

Diep has earned a reputation as a moderate Republican during his first year in Sacramento. He voted in support of a bill that removes mandatory sentence enhancements for some repeat criminals and as he’s spoken out against President Donald Trump’s immigration policies. Since voter registration data shows the GOP is losing ground in the area, and many recent immigrants or relatives of immigrants live in the district, those stances could position Diep to win back his seat.

But Baugh accused Diep of preparing to leave the Republican party. And he argued in one of this emails to fellow county Republicans that it wasn’t fair for the party to stand by Diep while it abandons 73rd District Assemblyman Bill Brough “for private indiscretions that he disputes.”

Brough is facing allegations of sexual assault and an investigation by state ethics officials over his use of campaign funds. Brough has repeatedly denied wrongdoing in both cases and is running for reelection, though state and local GOP leadership has thrown its support behind Republican challenger Laurie Davies.