According to the latest CBS News/YouGov Battleground Tracker, the Republican Party is split over President Trump: 55 percent say they are with Trump, “period" while another 32 percent say they support him, so long as he delivers what they want.

These figures contrast sharply with the 78 percent of Democrats who are against Trump, “period" and the 14 percent who say they are against him, but would be "willing to reconsider, if he does a good job." Trump's opponents are more united than his backers.

Reshaping his party's coalition, Trump has accelerated the defection of women, minorities, young people, and college-educated white voters from the Republican Party. That said, Pennsylvania's suburban counties offer some interesting data that suggest the changes are not taking place in as uniform a fashion as the top-line poll numbers seem to indicate.

One statistic reported by the Pennsylvania Secretary of State's Office is the number of people in each county who change their party affiliation from Republican to Democrat and from Democrat to Republican. Over the last six years, Republicans have garnered the majority of the party switchers, averaging about 60.5 percent of the voters who swapped affiliations between the two major parties. This GOP advantage among party switchers shouldn’t be too much of a surprise, in that Democrats tend to garner a larger share of newly registered voters because of their partisan advantage among young people. Hence, new voters mostly start out as Democrats, and over time some switch affiliations and become Republican.

Even though the total number of these voters is not large (about 58,000 each year out of more than 7.27 million registered voters for the two major parties), these switchers can be viewed as a leading indicator of public sentiment. Expressed another way, with all candidates on the ballot in a general election, one can easily vote for someone from a different party. Those who take the time to officially switch their voter registration from one party to another are either so moved by events (or a candidate) that they feel the need to don a new partisan identity or they desire the opportunity to vote in their new party's closed primary election. Both motivations may be present at the same time. What makes these party switchers interesting is that either way, they tend to be highly engaged voters.

When one looks at the county level, it is clear that while Republicans have won the larger share of Pennsylvania party switchers, the Democrats have still won in the urban areas. For instance, in Philadelphia County during the last six years, Democrats have averaged about 56.5 percent of party switchers. Strikingly, in 2016, Republicans managed to win about 56 percent of party switchers, but over the last six months of 2018, they have only won 11 percent. In short, Philadelphia Republicans are becoming Democrats at a very fast clip.

The two charts below track the last six years of switchers between the two major parties in the mostly suburban counties that surround Pennsylvania's two major cities. The first chart shows the four counties that surround Pittsburgh. As can be seen, Republicans are winning a larger percentage of party switchers in these counties than in the overall state. While there has been some variation over time, with an uptick occurring in the lead-up to the presidential election (between 2015 and 2016), Republicans continue to garner about 70 percent. The second chart shows the four counties surrounding Philadelphia. In addition to generally trending below the state average, it is notable how far the Republicans have fallen in the last two years. In all four counties, Democrats are now winning the majority of party switchers.

Overall what these data suggest is that in the western part of the state, Trump and the Republican Party remain popular and former Democrats want to join their cause. In the eastern part of the state, it seems that the love affair with the Republican Party that peaked in 2016 is now over. In short, Trump's base may well be shrinking: "the number of people who identified as Republican were about 2 percentage points smaller than in 2017."

The two states of the Republican Party in Pennsylvania likely won't be evident until 2020, but these trends suggest that Trump took over the GOP at its peak strength and that he has made it weaker, not stronger. By the time Trump runs for re-election, his path, which had already relied on a few more votes in the few key states, looks even more improbable now.



