ABC News’ Teddy Davis reports: Indiana Republican Congressman Mark Souder, a staunch family values conservative who was elected as part of the Republican Revolution of 1994, has told colleagues that he is resigning his seat in the U.S. House of Representatives amid an affair with a part-time member of his staff. "It is with great regret I announce that I am resigning from the U.S. House of Representatives as well as resigning as the Republican nominee for Congress in this fall's election," said Souder. "I sinned against my God, my wife and my family by having a mutual relationship with a part time member of my staff," Souder added. "I am so shamed to have hurt those I love." Souder’s decision to step down comes two weeks after he survived a Republican primary challenge from car dealer Bob Thomas. In the GOP primary, Souder received 48 percent of the vote. Thomas received 34 percent of the vote. A third candidate, Phil Troyer, received 16 percent of the vote. A fourth candidate, Greg Dickman, received 3 percent of the vote. Souder’s resignation, which was first reported by Fox News, was trumpeted Tuesday morning in an “in case you missed it” e-mail from the Democratic Congressional Campaign Committee. Democratic officials acknowledge, however, that Souder’s resignation will not improve their chances of carrying this solidly Republican district. In the 2008 presidential race, at a time when Barack Obama was carrying the state of Indiana as a whole, John McCain won the district by 13 points – 56 to 43 percent. “The filing deadline has passed and this is NOT a competitive seat,” according to a Democratic official who was granted anonymity in order to be more candid about the party’s prospects. The Democratic nominee is Dr. Tom Hayhurst. He was the Democratic nominee in 2006. The third congressional district of Indiana covers the Fort Wayne area in northeast Indiana. Souder’s resignation, which he is submitting to House Speaker Nancy Pelosi, D-Calif., will become effective this Friday. Souder's expected resignation follows the March resignation of New York Democratic Congressman Eric Massa who resigned amid allegations that he sexually harassed male staffers. Massa's case is now before the House Ethics Committee. ABC News’ Matt Loffman contributed to this report.