Democrats are pushing hard to flip six Republican-held House seats in California, and in a Los Angeles Times/UC Berkeley's Institute for Governmental Studies (IGS) poll released Thursday, they are leading or tied in all six. "The Democratic tide threatens to swamp congressional districts in Southern California's suburbs that Republicans have controlled for decades," boosting Democrats' hopes of winning the House in November, the Times says. "But if the tide ebbs only slightly, the GOP could emerge with much of its control intact." Voting by mail begins on Monday.

The unpopularity of President Trump "appears to be the main motivator for voters in these districts," said Mark DiCamillo, the Berkeley IGS poll director. "He's the central figure." But the GOP's strategies — painting opponents as too liberal, banking on a gas tax repeal to boost support — seem to have mostly fallen flat, the Times says.

The biggest pickup opportunities for Democrats are California's 49th and 45th Congressional Districts, in Orange and San Diego counties, the poll found. In the 49th, represented by retiring Rep. Darrell Issa (R), Democrat Mike Levin has a 55 percent to 41 percent lead over Republican Diane Harkey. Rep. Mimi Walters (R) in the 45th District trails Democratic challenger Katie Porter, 45 percent to 52 percent. In the 48th District, Rep. Dana Rohrabacher (R) and Democrat Harley Rouda are tied at 48 percent apiece, Democrat Gil Cisneros is leading Republican Young Kim by 1 point in the open 39th District, Democrat Katie Hill leads Rep. Steve Knight (R) by 4 points in the 25th District, and in the Central Valley's 10th District, Rep. Jeff Denham (R) trails Democrat Josh Harder, 45 percent to 50 percent.

The poll also found Rep. Devin Nunes (R) leading Democratic challenger Andrew Janz 53 percent to 45 percent, and indicted Rep. Duncan Hunter (R) ahead of Democrat Ammar Campa-Najjar 49 percent to 47 percent. The Berkeley IGS poll surveyed 5,090 likely voters online Sept. 16-23, and the margin of error ranges from ±4 points to ±6 points. Peter Weber