That bedrock belief, which Republicans and Democrats had shorthanded to "the Blue Wall," was torn asunder as Trump romped through a series of Great Lakes states that had been Democratic cornerstones for decades. A trio of reliably Democratic states won by Trump, or with a Trump lead as of Wednesday morning -- Wisconsin, Michigan and Pennsylvania -- were never assumed to be a given, but every Clinton path to the White House took the Blue Wall as the starting point for any path by Hillary Clinton to 270 electoral votes. A fourth, Minnesota, showed just a slim lead for Clinton, and was too close to call by Wednesday morning.
The 18 states and the District of Columbia that have supported Democrats for president since 1992 gave Democrats 242 electoral votes -- placing Clinton only 28 votes away from clinching the nomination. Analysts on both sides of the aisle spent most of the past months devising the path of least resistance for obtaining that margin.
Tuesday made that exercise a fool's errand. Trump outright won two of the three -- Wisconsin and Pennsylvania -- and leads narrowly in the third, Michigan.
The last time Republicans won in Wisconsin? 1984.
The last time they won Michigan? 1988.
The last time in Pennsylvania? Also 1988.
And the last time Minnesota went red? 1972.
Powered by an energized white working-class who dot small towns across those states, a Republican wave swept across and crumbled that wall. Trump's message on trade channeled a dissatisfaction with the de-industrialization that has changed the economy in the Rust Belt, and results show that it resonated on Tuesday evening.
His voters showed up.
Clinton was also not as popular with white voters as Obama was. She won only 37% of the white vote, compared to Obama's 39%. Surprisingly, Trump also garnered a slightly smaller share than Mitt Romney, capturing 58% of the vote to Romney's 59%.
Republicans have striven for cycles to flip some of those states, particularly George W. Bush, who made efforts during his presidency to take Wisconsin and Pennsylvania. But their position behind the wall was fortified each time GOP candidates tried to win them -- and failed.
Democrats, too, took the states largely for granted this cycle.
Pennsylvania, to be sure, was pegged as a top-tier battleground from virtually the first day of the general election. Clinton did not visit Wisconsin a single time after the Democratic National Convention, and the state was not targeted for advertising during the final weeks. Pundits mocked Trump's last-minute trip to Minnesota. trAnd Michigan was largely overlooked for the entire race, scrambling in the final days to bring Clinton and President Barack Obama in a last-ditch effort to protect their turf.
By that point, it appears, it was too late.