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FONTANA, Calif. (KABC) -- In San Bernardino County, early voting is underway at a brisk pace for California's Nov. 4 Proposition 50 special election. The ballot measure puts forth a redrawn congressional map that could net Democrats five House seats. Introduced by 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. "It had to happen very quickly," said San Bernardino County Registrar of Voters Joanna Finwall. "What normally we take three or four months to put together, we had to do in about a month and a half. The most important thing was to find our polling locations and to have those set. "We did all of the same work on a much expedited time frame," Finwall said. " But we're ready." As of Thursday, according to the county registrar's office, at least 18% of ballots that were sent out have already been cast by voters. In San Bernardino County, voters can visit any of the six early voting locations listed below to vote early or to drop off a completed and unsealed mail ballot: San Bernardino County Registrar of Voters Office, 777 E. Rialto Ave., San Bernardino Monday - Friday from 8 a.m. to 5 p.m. Saturday, Nov. 1, from 8 a.m. to 5 p.m. Election Day, Tuesday, Nov. 4, from 7 a.m. to 8 p.m. Closed Sunday, Nov. 2 Town of Apple Valley Recreation Center, 14955 Dale Evans Pkwy., Apple Valley Thursday - Monday from 10 a.m. to 6 p.m. Election Day, Tuesday, Nov. 4, from 7 a.m. to 8 p.m. Closed Sunday, Nov. 2 Joshua Tree Community Center, 6171 Sunburst St., Joshua Tree Thursday - Monday from 10 a.m. to 6 p.m. Election Day, Tuesday, Nov. 4, from 7 a.m. to 8 p.m. Closed Sunday, Nov. 2 Fontana Lewis Library & Technology Center, 8437 Sierra Ave., Fontana Thursday - Monday from 10 a.m. to 6 p.m. Election Day, Tuesday, Nov. 4, from 7 a.m. to 8 p.m. Closed Sunday, Nov. 2 Ontario Conference Center, 1947 E. Convention Center Way, Ontario Thursday - Monday from 10 a.m. to 6 p.m. Election Day, Tuesday, Nov. 4, from 7 a.m. to 8 p.m. Closed Sunday, Nov. 2 Victorville City Hall, 14343 Civic Dr., Victorville Thursday - Monday from 10 a.m. to 6 p.m. Election Day, Tuesday, Nov. 4, from 7 a.m. to 8 p.m. Closed Sunday, Nov. 2 Congressional district lines are normally redrawn each decade after the U.S. Census. 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. 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.