The improbable run of Democratic 16th Assembly District candidate Rebecca Bauer-Kahan continued to gain steam Tuesday after updated results posted by the Alameda County Registrar of Voters knocked Republican Assemblymember Catharine Baker’s precarious lead to 339 votes.

Since the Nov. 6 election, Bauer-Kahan, a first-time candidate, has consistently whittled away Baker’s modest advantage. It’s a trend that has many East Bay Democrats ebullient, but cautious since few had this type of an upset on their radar.

“We are very encouraged by what we see in Catharine Baker’s dwindling lead and the number of votes Rebecca is winning in Contra Costa County,” said Angela Ramirez Holmes, chair of the Tri-Valley United Democratic Campaign. “We expect this trend to continue.”

The latest results show Baker with 83,813 votes, or 50.1 percent of the vote, to Bauer Kahan’s 83,474, or 49.9 percent.

Baker’s advantage had shrunk to 526 votes on Monday following a holiday update by the Alameda County registrar’s office. The Contra Costa County Registrar of Voters last updated their results on Nov. 9. Another update is scheduled to be posted this Friday.

Bauer-Kahan, a Lamorinda resident, holds a narrow advantage in Contra Costa County, while Baker leads in Alameda County. But the difference in Alameda County continues to drop. More than 75,000 ballot remain uncounted in Alameda County. As of last Friday, 108,000 remain in Contra Costa County.

Despite the surprising developments, there were hints that  Baker’s re-election might be vulnerable. The Contra Costa County and Tri-Valley district’s perennially unfavorable voter mix for Republicans and the threat of a blue wave prompted by opposition to President Trump surely posed problems for the East Bay’s lone GOP state legislator.

But few imagined Bauer-Kahan, who had lost the head-to-head June primary to Baker with a smaller portion of the vote than the Democrat in the 2016 General Election, had a viable chance to even come close to unseating the incumbent until internal polling in early October indicated the race was a dead heat.

Bauer-Kahan’s campaign began a concerted effort link Baker to Trump. A 30-second campaign video aimed to remind voters of Baker’s party affiliation in a district where even independents registered as No Party Preference outpace Republicans.

The California Democratic Party, which in the previous two cycles had been defeated by Baker, sensed an opening, and inundated voters with mailers reinforcing Baker’s party registration.

It remains to be seen whether a late spate of mailers from Baker slamming Bauer-Kahan will be enough to stave off a stunning upset. Before Baker was elected in 2014, a Republican had not represented the East Bay in the state legislature since 2008.