The blue wall was Kamala Harris' clearest path to the White House. Here's why it faded away.

• Democrats hoped Vice President Harris could win the White House through the blue wall.
• But once again, Donald Trump made inroads in three key states and flipped them into the GOP column.
• Harris would have secured the presidency if she had won Michigan, Pennsylvania, and Wisconsin.

Shortly after Vice President Kamala Harris launched her presidential campaign, one of her first stops was in West Allis, Wisconsin. The Milwaukee suburb made up a small piece of the electoral puzzle in a state where elections are decided by the slimmest of margins.

Harris repeatedly made stops in Wisconsin, Michigan, and Pennsylvania during her campaign. These states were part of the "blue wall," or the set of states that Democratic presidential nominees all won between 1992 and 2012.

In 2016, Donald Trump breached that wall, winning all three states and blocking former Secretary of State Hillary Clinton from the White House. President Joe Biden in 2020 won all three states with Harris as his vice-presidential running mate.

This year, Harris was shut out. Trump won all three, securing the Oval Office once again.

Here's why Harris ultimately faltered in the trio of blue wall states.

Navigating a difficult path

Ultimately, Harris lost Michigan, Pennsylvania, and Wisconsin by narrow margins.

To secure the presidency, candidates must win at least 270 Electoral College votes, and Harris won 226 to Trump's 312. She came up short by 44 electoral votes, which she could have earned had she won Michigan (15 votes), Pennsylvania (19 votes), and Wisconsin (10 votes).

Trump defeated Harris in Michigan by 1.4 points (49.7% to 48.3%). According to the latest results, the president-elect won Pennsylvania by 2.1 points (50.6% to 48.5%). And in Wisconsin, Trump defeated Harris by a 0.9-point margin (49.7% to 48.8%).

These weren't blowouts, but even a small shift was enough to hand Trump the election.

Also, Harris didn't win any other major swing states this year, which made it mathematically impossible for her to get to 270 electoral votes after the blue wall fell and GOP-leaning states stayed true to form.

Harris' suburban performance wasn't strong enough

Democrats went into the election hoping to make historic gains with suburban voters. The party believed those voters would continue to reject Trump's political brand as they did in 2018, 2020, and 2022.

However, unlike 2020, when Biden won the suburbs by two points (50% to 48%) nationally, Trump this year won suburban voters by four points (51% to 47%), according to exit polling conducted by Edison Research.

In the blue wall, Harris performed well in many key counties, including Oakland County, just outside Detroit; Montgomery County, Pennsylvania, an affluent county adjacent to Philadelphia; and Dane County, which includes the Wisconsin capital of Madison and its surrounding areas.

But it wasn't enough to offset Trump's rural and exurban strength, as well as his better-than-expected retention of support in critical areas like Waukesha County, Wisconsin, a suburban jurisdiction close to Milwaukee, and Bucks County, Pennsylvania, a crucial swing county near Philadelphia. Harris also had to overcome Trump's increased vote share with minority voters — notably among Black men and Latinos — which cut into her margins in many cities.

For example, Harris won Oakland County by 10 points. But Biden won it by 14 points in 2020. In a populous county filled with the sort of college-educated independents and disaffected Republicans that the Harris campaign was targeting, the vice president's margins had to be higher to counter Trump's gains in places like Saginaw County, Michigan — a politically competitive jurisdiction that he won this year after losing it to Biden four years ago.

Harris was also hurt by anger over Biden's handling of the conflict in Gaza. Many Arab American voters in Dearborn — a city just outside Detroit — flipped to Trump.

The union vote wasn't united behind Harris

After Biden stepped aside as the Democratic presidential nominee in late July, Harris was tasked with running a 107-day campaign. This involved broadening her profile and forging relationships with leaders accustomed to the president.

While Harris was enthusiastically backed by myriad public-sector union leaders and large shares of their members, she also had to contend with non-endorsements from the Teamsters and the International Association of Fire Fighters. Within the latter set of unions, many rank-and-file members backed Trump, despite Biden's strength with many of these members just four years ago.

Organized labor is crucial for Democrats in the blue wall, and Harris' support wasn't deep enough to eclipse Trump's inroads.

In Wisconsin, Trump won 51% of union households, compared to Harris' 49%, according to Edison Research.

Harris won union households in both Michigan (58% to 40%) and Pennsylvania (54% to 45%), but it still wasn't enough to win those states.

Harris sought to craft her economic message around the needs of working-and- middle-class Americans — which included union workers — but Trump had an advantage on the issue that lasted through Election Day.

According to CNN's exit polling, the economy was the most important issue for 32% of voters, and those voters broke for Trump by an overwhelming 80% to 19% margin.