PHILADELPHIA - Sandy Arnell used to work for Republican lawmakers in Washington and in Harrisburg, Pennsylvania's capital. She considered herself to be liberal on issues like abortion but conservative when it came to fiscal issues. She didn't always vote Republican. But she identified as one, and voted in GOP primaries.
Arnell, of Downingtown, had already been drifting from conservative politics before Donald Trump was elected president. But she reached a breaking point with what she called the "hatred and negativity" of his presidency and became a Democrat.
"I was holding on to my Republican card, literally and metaphorically, with a firm grasp," said Arnell, 48. "And I just sat down at the computer one day and I just went on the Chester County website and that's it.
"I'm done," she said. "I'm disgusted."
Arnell represents the political transformation of Philadelphia's suburbs, now largely Democratic and mobilizing against Trump in the final six weeks before the election. While Trump narrowly won America's suburbs in 2016, Hillary Clinton swept Philadelphia's four collar counties. It wasn't enough to stop Trump from narrowly winning the state, and with it the White House. But people like Arnell who had been slowly walking away from the party in these onetime Republican strongholds broke into a sprint after 2016, and they haven't looked back.
Registered Democrats outnumber Republicans in all four counties, and by wide margins in two. Democrats won all but one suburban congressional seat in 2018. And they won control of all four county governments last year - in one case for the first time since the Civil War.
There's little doubt that Democratic nominee Joe Biden will defeat Trump in the Philadelphia suburbs. The question is whether he'll do so with big enough margins. Voter registration trends and interviews with dozens of voters over the last two months suggest Trump retains strong political support in the longtime Democratic bastions in small Rust Belt towns throughout Northeastern and Southwestern Pennsylvania that he won in 2016.
That means Biden's path to victory, in a state increasingly seen as one of the most critical 2020 battlegrounds, relies on racking up big wins in the populous southeast. About 21% of Pennsylvania's registered voters live in Bucks, Chester, Delaware, and Montgomery Counties.
"To win the state he has to do better than" Clinton did in the suburbs, said J.J. Balaban, a Democratic consultant in Philadelphia. "It is certainly possible, if not likely, that Biden will do worse than Hillary in certain rural parts of Pennsylvania. ... Doing better in the suburbs does not guarantee victory statewide."
Trump has tried to draw back suburban voters by arguing in often apocalyptic language that Biden will "destroy" the suburbs. He has warned the looting in American cities could come to suburban cul-de-sacs, made appeals to racist fears of expanded affordable housing, and tweeted that "suburban housewives" will vote for him.