Republican Charlie Dent is a former US congressman from Pennsylvania who served as chairman of the House Ethics Committee from 2015 until 2016, and chairman of the House Appropriations Subcommittee on Military Construction, Veterans Affairs and Related Agencies from 2015 until 2018. He is a CNN political commentator. The views expressed in this commentary are his own. View more opinion on CNN.

(CNN) While much of the 2019 election discussion focused on the Kentucky and Mississippi gubernatorial contests and the Virginia state legislative races, there were pivotal countywide races in Pennsylvania that provide a much clearer view of the political realignment we have been slowly witnessing for many years in my home state.

Charlie Dent

The lesson learned from Pennsylvania, which went for Donald Trump in 2016, is the same as for the rest of the country. As a result of his election and performance in office, the suburbs are nearly completely gone for the Republican Party.

When I was first elected to the Pennsylvania House of Representatives in 1990 from an Allentown-based district, Republicans performed very well in the suburbs and dominated rural areas. There were even a few Republicans like me who were winning elections in urban areas and even more Democrats who were successful in rural communities throughout the state and well beyond the Philadelphia region.

But things were slowly changing. In 1990, while I and two other Republicans were defeating entrenched Democratic state House incumbents in the Lehigh Valley, a perennial bellwether and swing region of eastern Pennsylvania, an almost unheard of young man and young woman defeated an entrenched Democratic congressman and Democratic state senator, respectively, from the other side of the state, in the Pittsburgh area. Their names: Rick Santorum and Melissa Hart.

Four years later Rick Santorum became a US senator, and ten years later Melissa Hart gained a seat in the US House of Representatives. These 1990 election results were shocking to the political class at that time. How did five Republicans defy political gravity to win Democratic districts in the midterm election during the Presidency of George H.W. Bush? This should not have happened, but what we were witnessing was an emerging trend.

Read More