Editor's note: The following column originally appeared in The Hill newspaper and on TheHill.com.

If “Low Energy” Jeb Bush was the GOP nominee, he’d be winning.

If “1 for 38” John Kasich was running against Hillary Clinton, he’d be ahead, too.

The same is true for “Little Marco” Rubio.

My bet is that if any of those three GOP primary candidates had won the nomination, they would by now have consolidated the Republican base by attracting educated, white voters — especially women — who have questions about Clinton. Many of those voters, however, cannot bring themselves to support the actual nominee of the Republican Party, Donald Trump.

The same dynamic affects independent voters, too. They might well be attracted to a Republican candidate — if the candidate in question was not known for refusing to release his taxes, mocking the disabled, demeaning women, hating immigrants, praising Vladimir Putin and lying about the Mexican president’s stand on a border wall.

Even so, at the moment Trump is drawing closer to Clinton. Having been behind by eight percentage points in early August he is now within about three percentage points, according to the Real Clear Politics average of polls.

Is there an “October Surprise” with the power to push one candidate to victory?

Yes — in the shape of President Obama.

A majority of Americans — 50.8 percent on average, according to the latest polls — approve of Obama’s job performance. In a new Washington Post/ABC News poll released Sunday, 58 percent of adults gave Obama the thumbs-up and only 40 percent disapproved of his performance. Such popularity for an incumbent commander-in-chief in the twilight of his presidency is truly remarkable in an era of polarization and widespread discontent with the political system.

Obama’s predecessor, George W. Bush, left office with a 22 percent approval rating in the last CBS/New York Times poll of his presidency. His poor ranking with voters led the last two Republicans who ran for the White House — John McCain in 2008 and Mitt Romney in 2012 — to conclude it was best to have nothing to do with Bush during their campaigns.

Something of a parallel was seen among Democrats in 2000. Then, Vice President Al Gore made a strategic decision to keep President Bill Clinton off the campaign trail because the incumbent, despite high approval numbers, was tainted by the Monica Lewinsky sex scandal.

But in this race, the incumbent president holds a winning hand. He is the key to unlocking support from the nearly 20 percent of voters who are undecided — the independents, conservative Democrats and college-educated Republicans who will be pivotal to the outcome of the election.

According to a Gallup poll published on August 30, 55.4 percent of Americans say they rate their life “well enough to be considered ‘thriving.’” That number has risen during Obama’s years in the White House.

Last month’s unemployment rate was 4.9 percent — near de facto full employment, according to most economists. The Affordable Care Act, in the face of constant Republican antagonism, has provided health insurance coverage to more than 20 million Americans who were previously uninsured.

The Dow Jones Industrial Average continues to shatter records, closing at over 18,000 again last week. The NASDAQ has more than tripled since Obama became president. Last week also brought news that the U.S. Consumer Confidence Index had reached its highest level since September 2015.

An August poll from Gallup showed that 48 percent of Americans approved of the way Obama is handling the economy. The economy is the number one issue for voters.

Last week, Trump dismissed the good economic indicators by claiming that the Federal Reserve was creating a “false economy” and an “artificial stock market.” But there is a strong sense on both Wall Street and Main Street that the economy has come back to life and Americans are benefitting. 

Meanwhile, Trump’s economic plan is getting dumped on by leading businessmen and policy experts.

“A Trump victory in particular could prolong and perhaps exacerbate policy uncertainty and deliver a shock (though perhaps short-lived) to financial markets,” said Willem Buiter, the Chief Economist for Citigroup, in a memo last month.

Put it all together and it becomes clear Obama can help Clinton capitalize on economic issues and stir Democrats to turn out.

“Most of [Obama’s] appearances will be timed to coincide with voter registration deadlines and the start of early voting,” according to a recent New York Times report.

The Times also wrote: “Neither the Clinton campaign nor the White House has announced any more appearances, in part because they want to be able to send Mr. Obama where they think they need him most. But his visits are likely to be concentrated in Florida, North Carolina, Ohio, Pennsylvania, New Hampshire, Nevada and Iowa, campaign officials said. Mr. Obama will generally campaign without Mrs. Clinton.”

It was announced last week that First Lady Michelle Obama would also be hitting the campaign trail for Clinton. The First Lady enjoys a 64 percent approval rating, according to the most recent Gallup survey.

Contrast the political dynamite available to the Clinton campaign — in the form of the Obamas — with the sorry roster of C-list surrogates the Trump campaign is leaning on.

With the exception of Alabama Sen. Jeff Sessions and a handful of obscure backbenchers in the House, the Trump campaign has hardly any Capitol Hill surrogates speaking on its behalf. Romney, McCain and Bush had a chorus of current lawmakers making the case for them during their campaigns.

The Hill identified five swing states last week where Obama could be the biggest help to Clinton: Iowa, Nevada, Florida, Pennsylvania and North Carolina.

The Obamas can also provide a boon to lackluster Democratic Senate candidates in these states who have fallen behind in the polls.

The president is doing more than being nice to a fellow Democrat. He needs Clinton to preserve his legacy and prevent Trump from taking a wrecking ball to his accomplishments. The Democrats in the House and the Senate need Obama to get his voters out to the polls one last time.

Delivering his one-time secretary of State a victory in November is likely to be one of Obama’s greatest political legacies.

Juan Williams is a co-host of FNC's "The Five," where he is one of seven rotating Fox personalities.