The Longshot Path for Donald Trump to Win 270 Electoral Votes

— -- Donald Trump’s path to the White House is fading fast.

With national polls showing Hillary Clinton growing her lead and Trump losing his grip on traditionally red states, Clinton looks likely to prevail on Election Day.

The Democratic nominee’s path to 270 electoral votes has room to spare; Clinton can afford to lose classic battlegrounds like Ohio and Florida as long as she holds onto light blue states like Pennsylvania and Colorado.

An ABC News analysis out today estimates Clinton is already poised to win at least 300 electoral votes –- even if Donald Trump wins every toss-up state.

Still, a very narrow four-step path to the GOP nominee's victory remains. But it won't be easy since Clinton threatens to disrupt this road at every turn, running even in the polls with Trump in must-win states like North Carolina, Ohio and Florida.

Even one wrong move would hand the White House to the Democrats for a third consecutive term. Trump must take all these steps in order to win the White House:

1. Retain Every State Mitt Romney Won in 2012

First, Donald Trump must hold every state that Mitt Romney won in 2012. This includes traditionally red states like Arizona and Georgia, where Bill Clinton won in 1996. In those states, Clinton has pushed the race so close that she is within the margin of error, according to recent polls.

In Utah, independent candidate Evan McMullin threatens to siphon off Mormon votes and win the state outright. But the most challenging state for Trump to hold might be North Carolina, where Mitt Romney won by just 2 percentage points in 2012 and a recent poll from CNN/ORC showed Clinton with 48 percent vs. 47 percent for Trump.

2. Win Ohio

No Republican candidate has won the White House without the state of Ohio. Indeed, Donald Trump must win the state, as well, to have a chance at the presidency. Early voting returns have shown encouraging signs for Trump, with fewer Democrats in the Buckeye State requesting absentee ballots this year than in 2012. Recent polling has shown Trump’s slim lead from late September fading away: A NBC/WSJ/Marist poll showed him with 42 percent vs. 41 percent for Clinton. Another poll from Quinnipiac University showed the race tied at 45 percent each.

3. Win Florida

Florida may be the best firewall for Hillary Clinton’s campaign. Two Quinnipiac University polls from the last three weeks have shown Clinton with a slim lead in Florida. Donald Trump hasn’t held a statistically-significant lead in a poll since July.

Early voting numbers look good for Clinton: they’ve cut their mail-in ballot deficit in half this year compared to 2012, according to early data.

"Certainly, the Clinton campaign feels very good about where they are with the mail-in ballot," election expert Michael McDonald told ABC News. Without a win in the Sunshine State, Donald Trump’s path to 270 electoral votes is virtually impossible.

4. Choose His Own Adventure: 17 More Electoral Votes

Even if Donald Trump makes it this far successfully, he still has to find another 17 electoral votes –- and his options are scarce. In all of the options, he trails significantly in the polls. Nonetheless, he’ll need one of these to happen in order to win. Here are the three best possibilities:

Win Pennsylvania. The population of working-class white voters in Pennsylvania seemed to present a good opportunity for Trump to take the state. But despite campaign stops and a last-minute flood of television advertising dollars, a recent poll from Bloomberg Politics shows Clinton with a 9-point lead. The state’s 20 electoral votes would be enough to push Trump across the finish line on its own. However, Pennsylvania hasn’t gone red since 1988.

The Small State Combination. A perfect combination of states with fewer electoral votes could also place Trump in the White House. Victories in all of the small states in play -- including Iowa, Nevada, New Hampshire and the second Congressional district of Maine -- would give Trump exactly 270 electoral votes. And although Iowa and Nevada appear within reach, a WMUR/UNH poll shows New Hampshire is leaning toward Clinton -- she’s ahead by a whopping 15 percentage points.

Wildcard State. Several other combinations, though very unlikely, exist to push Trump across the finish line. Winning just one unexpected state could push Trump over the top. However, recent polling in light blue states like Wisconsin, Virginia, Michigan and Colorado show little doubt that they will land in Clinton’s column. In addition, Trump hasn’t spent significant time or resources in these states.

The wildcard options include: 1) winning Wisconsin, the second Congressional district of Maine, plus either Nevada or Iowa 2) winning Virginia and either Nevada or Iowa or New Hampshire 3) winning Michigan and the second congressional district of Maine and 4) winning Colorado, Iowa and either Nevada or New Hampshire.