Democrat Jessica Cisneros says the final vote tally in her runoff against U.S. Rep. Henry Cuellar likely won’t be known until the beginning of next week.

Just 177 votes separated Cuellar and Cisneros on election night Tuesday. The two are competing for the Democratic Party’s nomination after Cisneros forced the longtime incumbent into a runoff in the March primary. The winner will face Republican Cassy Garcia, who won her party’s runoff Tuesday.

Cuellar declared victory in his runoff on Twitter that night, saying, “The votes are in, the margin will hold.”

But Cisneros expressed confidence Thursday that the winner has not been determined yet.

“We are within reach to go on and win this thing,” Cisneros said on a conference call with reporters. 

“It’s been very clear that there’s still hundreds of uncounted mail-in ballots and provisional ballots across Texas 28,” said Cisneros. “The information that we’ve been receiving is that due to the long holiday weekend, it looks like many of these ballots are not going to be counted until next week.”

Cuellar’s campaign did not immediately respond to an email requesting comment.

Cisneros has continued fundraising since the election, telling supporters in an email Wednesday that she needed “resources” to “fully fund this recount effort.” She has not yet petitioned the Texas Secretary of State for a recount.

Under state law, mail-in ballots must be received by county election departments by 7 p.m. on election day for them to be eligible to be counted. If a ballot is postmarked by 7 p.m. on election day, it can still be counted if it was received by the elections department by 5 p.m. Wednesday.

The 28th Congressional District encompasses all or part of nine counties, stretching from Bexar County south along the border to Starr County and includes Cuellar and Cisneros’ hometown of Laredo in Webb County.

Cisneros cleaned up in Bexar County on Tuesday night. She took roughly 86% of the votes there, up from the 67% she took in Bexar County in March

Michelle Tremillo, executive director of the Texas Organizing Project, told the San Antonio Report that groups supporting Cisneros knocked on over 78,450 doors across the district, including roughly 49,000 in Bexar County.

Cisneros campaign spokesman Alejandro Garcia said the campaign did not have information about which counties had potentially uncounted ballots.

Cisneros said her campaign is reaching out to voters and asking them to track their mail-in ballots online to make sure they were counted. 

“If [the mail-in ballot] was rejected, we’ve been asking people to reach out to our campaign team or voter protection hotline … so that we can help them cure it,” she said.

Texas law allows voters whose mail-in ballots are rejected to correct certain errors within six calendar days of the election.

Andrea Drusch writes about local government for the San Antonio Report. She's covered politics in Washington, D.C., and Texas for the Fort Worth Star-Telegram, National Journal and Politico.