California Proposition 50 will pass, ABC News projects

If Prop 50 passes, some congressional districts won't change, but others would disappear -- like Republican Ken Calvert's district, which would move from Riverside County to L.A. County.

Instead, voters in Downey and Norwalk would decide who represents them in the new district. Many of those voters are liberal.

Calvert would most likely face a steep uphill battle to retain his congressional seat, which he has held for more than 30 years.

Watch more:

If Prop 50 passes, some congressional districts won't change, but others would disappear -- like Republican Ken Calvert's district, which would move from Riverside County to L.A. County.

Although California voters still have several more hours to cast their ballot, counting is already underway across the state.

At the San Bernardino County Registrar of Voters, things were in full swing as workers processed mail-in ballots.

Employees wearing a yellow vest are the only people that are allowed to handle any of the ballots that have been returned so far.

At the San Bernardino County Registrar of Voters, things were in full swing as workers processed mail-in ballots.

"I think we've received, to date, 295,000 mail ballots returned, and those have already gone through this process, have been scanned. We're hoping to see at least that much, if not a little bit more, tonight," said Joani Finwall, the San Bernardino Registrar of Voters.

Every ballot is scanned in a high-speed scanner, which detects voter signatures that are written on the ballot.

"Some of the signatures, the ones that are easy matches, go and ahead and get matched by this machine," said Joani Finwall, the San Bernardino Registrar of Voters. "And the others that... need the human eye, we have done manually."

Voting locations statewide close at 8 p.m., and officials expect the first batch of results to come in shortly after that.

A new poll shows that likely California voters favor Proposition 50, a ballot measure that puts forth a redrawn congressional map that could net Democrats five House seats.

According to a Public Institute of California (PPIC) poll published Wednesday, 56% of likely California voters say they will vote for Prop. 50 in the special election, and 43% are against it.

There are significant partisan differences in the numbers, with 84% of Democrats in support of the ballot measure, while 89% of Republicans say they will not vote for it. Independent voters appear to be leaning toward the left, with 55% responding affirmatively to the proposition, PPIC found.

Introduced by California Gov. Gavin Newsom and passed by the state legislature in August, the proposed map could give Democrats the opportunity to flip five Republican-held seats. Prop 50 came in retaliation to Texas' mid-decade redistricting, where Republican-friendly maps passed into law this summer could net the GOP five House seats.

Congressional district lines are normally redrawn each decade after the U.S. Census.

Most likely voters also stress the importance of Prop 50, with 68% saying the outcome of the ballot measure is "very important" to them, and 22% saying "somewhat important."

Newsom, considered a possible 2028 presidential candidate, has championed Prop 50 as an opportunity to "fight back" against Trump, who pushed Texas' redistricting efforts, and the ballot measure could raise his national profile.

California likely voters were mostly supportive of Newsom's leadership in the poll, with 55% saying they approve of his overall performance as governor.

Prominent political figures have joined forces with Newsom and thrown their support behind the ballot initiative, including former President Barack Obama, who rallied alongside the governor to champion the measure. In addition, Rep. Alexandria Ocasio-Cortez, D-N.Y., and Sen. Elizabeth Warren, D-Mass., cutting ads in favor of it.

California was the first Democratic state to enter the redistricting battle, with Virginia Democrats following suit last week and announcing plans to attempt to redraw maps as well. On Wednesday, the Virginia House of Delegates passed a constitutional amendment on redrawing congressional maps, according to ABC affiliate WRIC, and the measure now moves to state Senate review.

Following Texas, other Republican-controlled states have also entered the redistricting battle -- Missouri and North Carolina have adopted new maps, while Utah and Indiana are in the process of redrawing theirs.

Some Democrats in Maryland and Illinois have called for their states to redistrict, but not all leaders have bought in. Earlier on Wednesday, the Maryland state Senate chose "not to move forward" with mid-decade redistricting, according to a letter obtained by ABC News.

A new lawsuit filed Monday seeks to redraw New York's congressional maps in favor of Democrats, with plaintiffs arguing that the current lines are unconstitutional for misrepresenting Black and Latino votes, according to The Associtated Press.

Legislators in Republican-controlled Kansas and Florida have also indicated that they are considering mid-decade redistricting.

ABC News contributed to this report.

Across California, voters are heading to the polls to make their voices heard and with more than 6.7 million ballots already returned, turnout is expected to be strong.

Across California, voters are heading to the polls to make their voices heard and with more than 6.7 million ballots already returned, turnout is expected to be strong.

Voters in the Bay Area, both for and against Prop 50 spoke on how they feel about the only question on the ballot.

"I can't believe we are voting on this, to be honest with you," said Jack Freethy, who is against Prop 50. "Our state legislature is out of control. That probably answers how I feel.

"I did read the review by Common Cause, and it was very impressive, they took a case all the way up to the Supreme Court," said Michael Rouppet, who supports Prop 50. "They appealed to the nation's institutions, and those institutions failed voters. So I think that in my conscious, I support Prop 50 with that in mind."