In an interview at the South by Southwest festival Monday, Georgia Democrat Stacey Abrams admitted she is “still very bitter” about her failed gubernatorial bid, and she “can’t prove” she would have won the November 2018 race.

“I’m still angry. I’m still very bitter. I’m still sad,” Abrams said of the race she narrowly lost to Georgia Secretary of State Brian Kemp. “I can’t prove I would have won, but we don’t know because of how he behaved.”

Abrams, who recently delivered the Democrat Party’s official response to President Donald Trump’s State of the Union address, said she refused to concede because it would validate that “the process is proper.”

The failed candidate for governor and her allies have accused Kemp of suppressing African-American and Democrat voters to win what was one of the midterm election’s most high-profile races. Abrams, who is out with a new book Lead from the Outside, recently launched Fair Fight Action, a group aimed at combatting voter suppression. In a federal lawsuit against Georgia officials, the group accused the state of grossly mismanaging its election system.

“Georgia is ground zero for voter suppression,” Abrams told attendees of the annual Austin, Texas, conference. “We had a secretary of state for ten years who took advantage of almost every single version of voter suppression you can imagine and he worked it altogether into a seamless system that gets you if he doesn’t think you should be voting.”

“We have to talk about voter suppression all the time,” she went on. “Republicans talk about voter fraud all the time” and “we believe it’s true even though there isn’t a shred of evidence. Voter suppression is insidious because it looks like it’s supposed to happen.”

In addition to rehashing her failed gubernatorial bid, Abrams also made news announcing she will not run for president in 2020, saying that the earliest she would launch a White House bid is 2028. “2028 would be the earliest I would be ready to stand for president,” she said.