Chairman Darrell Issa (R-CA) speaks during a House Oversight and Government Reform Committee hearing on Capitol Hill, October 24, 2014 in Washington, DC. The committee is hearing testimony from officials regarding the Ebola crisis and the coordination of the multi-agency response. (Photo by Mark Wilson/Getty Images)

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SAN DIEGO -- A congressional seat thought to be safely in the hands of a powerful Republican incumbent is surprisingly in play after a strong showing by a little-known Democratic challenger in Tuesday's Primary Election.

Retired Marine Col. Doug Applegate mounted the challenge for incumbent Darrel Issa's seat representing the 49th Congressional District. Issa, who is the richest man in Congress, has held the seat for 15 years. Issa was thought to have a lock on his office, but the heavy Democratic turnout Tuesday pushed Applegate to within 6,200 votes of the incumbent. Issa out-polled Applegate, 51 percent to 45 percent, but the close finish surprised many political observers.

“I haven’t looked at the numbers closely, because I’m in this to win this,” Applegate said. "This is now a real candidacy. If Darrell Issa was asleep, he’s awake now.”

Issa was unavailable for comment, but his office release this message.

“Congressman Issa is honored to have received a solid majority of votes in yesterday’s election, enjoying a margin of nearly 6% over his nearest competitor, particularly in an election where an incredible number of Democrat voters turned-out to register a vote of protest against their party’s leading candidate. As always, Congressman Issa will campaign on his record of significant accomplishment and a philosophy which supports job creation and calls for government to be accountable and transparent to the people it represents.”

Now Democratic supporters are lining up behind Applegate to try to capture the coveted 49th District seat in the November election.