(CNN) It was where "good Republicans go to die," Ronald Reagan often quipped.

Now, with the final ballots counted, Democrats have achieved a total takeover of congressional seats in the one-time Republican bastion of Orange County.

Across the country on Election Day, Democrats shifted the balance of power in the US House by capturing the college-educated suburbs once dominated by Republicans. But there is no pocket of America where the erosion in GOP support is more striking than Orange County.

Laboring against a strong tide of disdain, and even disgust, for President Donald Trump, Republicans lost their grip on the wealthy enclaves along the coast in northern Orange County that comprise the district held by 15-term Rep. Dana Rohrabacher. They lost by a much larger margin along the coast farther south in the district of retiring Rep. Darrell Issa, which includes the San Clemente home where Richard Nixon holed up to write his memoirs after resigning from the White House.

On the days leading up to Election Day, GOP officials had been slightly more optimistic that they would hold the inland Orange County district represented by GOP Rep. Mimi Walters, who had served as the deputy chair of the National Republican Congressional Committee in Washington. But Walters conceded to her rival, UC-Irvine law professor and Elizabeth Warren protégé Katie Porter late last week after the latest batch of ballots counted by election officials made a GOP victory seem impossible.

Read More