This coastal Southern California district, one of the tightest races in the country, pits incumbent Republican Dana Rohrabacher against Democrat Harley Rouda, a lawyer and real estate businessman.

According to a recent New York Times/Siena College poll, the race is a dead heat, with both Rouda and Rohrabacher drawing 45 percent of the vote.

An affluent patch of Southern California, the 48th District has been a traditional Republican stronghold. The GOP holds a 10-point advantage in voter registration. But Hillary Clinton won the district by 2 points.

The most recent data show that political action committees have spent a scant $150,000 each. But Rouda has plowed some $1.2 million of his own money into the race while most of Rohrabacher's $1.7 million has come from large individual donations.

Rouda was endorsed by both progressive groups and the mainstream Democratic Congressional Campaign Committee in a contested primary. Rohrabacher voted to repeal and replace the Affordable Care Act, but voted against the tax reform bill.