(CNN) Two weeks from today, voters in western Pennsylvania will go to the polls to choose their next member of Congress. It might just be the most important race no one is paying attention to right now.

On its face, Pennsylvania's 18th District isn't much of a Democratic target. Donald Trump won the district by 20 points in 2016 and Mitt Romney carried it by 17 in 2012. Republican Rep. Tim Murphy had held it easily since 2002; he was unopposed in 2014 and 2016.

But Murphy was forced out of Congress in October when reports surfaced that he had urged a woman with whom he was having an affair to get an abortion.

That forced this special election. Republicans chose state Rep. Rick Saccone as their nominee, Democrats picked prosecutor and veteran Conor Lamb.

From the start, Republican insiders were worried about the candidate contrast: Saccone is a 60-something-year-old state legislator, Lamb is a 30-something Marine.

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