Republican presidential nominee Donald Trump says he feels guilty that he never served in the military – and his comments over time show just how uncomfortable the issue makes him. (Peter Stevenson/The Washington Post)

Republican presidential nominee Donald Trump says he feels guilty that he never served in the military – and his comments over time show just how uncomfortable the issue makes him. (Peter Stevenson/The Washington Post)

Democrat Hillary Clinton will spend the final days of the election trying to protect her lead in key battlegrounds, reflecting a tightening, unusually volatile race against Republican Donald Trump.

Trump, whose electoral college prospects are narrower, is banking on a late-hour attempt to win at least one blue-leaning state — and to dramatically drive up turnout in rural areas in a collection of battlegrounds where he must prevail on Tuesday.

With four days left on the campaign trail, both candidates and surrogates blitzed across the country Friday, making stops in states where polls have narrowed in recent days. The frenzied final days also include celebrity appearances — Jay Z and Beyoncé headlined a get-out-the-vote show with Clinton in Cleveland, and Stevie Wonder played a “Love Trumps Hate” show on her behalf in Philadelphia — and endless ads airing in battleground states.

Clinton stopped on Friday in Pennsylvania and Michigan, two states where she has consistently led Trump, as well as Ohio. She brought a new urgency to her message at a rally in Pittsburgh, focusing on the danger that she said a Trump presidency would present to the country and asking supporters to imagine Trump taking the oath of office in front of the Capitol and being in charge of the nation’s nuclear arsenal.

“Think about what it would mean to entrust the nuclear codes to someone with a very thin skin who lashes out at anyone who challenges him,” Clinton said. “Imagine how easy it would be that Donald Trump would feel insulted and start a real war, not just a Twitter war at 3 in the morning.”

Democratic presidential nominee Hillary Clinton called on supporters to vote and volunteer in the final days of the election. Rapper Jay Z closed the concert by performing his 1998 single "Hard Knock Life." (Victoria Walker/The Washington Post)

Clinton urged supporters to stage “an intervention” with friends and family members who plan to vote for Trump by explaining to them that “anger is not a plan.”

“Sometimes the fate of the greatest nations comes down to a single moment,” Clinton said. “This is one of those make-or-break moments for the United States. This is in your hands.”

[Clinton up 47-44 in Post-ABC News Tracking Poll, despite Trump’s 9-point edge on dealing with corruption]

Trump continued a tour of small towns in rural counties on Friday, first stopping at a country club in Atkinson, N.H. He continued to Wilmington, Ohio, between Cincinnati and Columbus. He planned to end the day in Hershey, Pa.

Besides reminding supporters of Clinton’s scandals, Trump focused on promises to return lost manufacturing jobs, protect residents from what he described as dangerous undocumented immigrants and get rid of crime in faraway major cities.

“Don’t let the pundits, the politicians or the media tell you what kind of a country you have,” Trump said in Wilmington. “Don’t let them limit your dreams because they want to limit your dreams. You can have any future you want.”

The final-days travel schedules of Trump and his running mate, Indiana Gov. Mike Pence, reflect a dire need to win vote-rich swing states including Florida and North Carolina, where Trump is to campaign on Saturday.

The latest Washington Post-ABC News tracking poll shows Donald Trump and Hillary Clinton in a dead heat nationally. (Peter Stevenson/The Washington Post)

Lately, Trump has made many stops in out-of-the-way places, most of which are already certain to break heavily for Republicans.

His advisers say they think he can win over rural white voters by a much bigger margin than Republican nominee Mitt Romney did in 2012 — and come away with significantly more votes, which they gamble will offset his weakness among suburban Republicans in battleground states.

As part of a bid to steal a blue-leaning Midwestern state, Trump is also set to return on Sunday to Wisconsin, a state that a Republican nominee has not won since 1984. The many white blue-collar voters in the state have raised hopes among Trump and his allies that he has a chance there.

Although Clinton, in contrast, needs only to hold on to leads in the states where she is ahead, she intends to fight for votes beyond those, her campaign manager, Robby Mook, said Friday.

“We built our operation for a wide map from the beginning of the campaign,” Mook said in a phone call with reporters.

And while Trump is trying to drive up turnout among white voters, Clinton is putting a premium on minority voters, who polls suggest are likely to break heavily in her favor.

Mook touted what he called “the Hillary coalition” — Latinos, Asians, African Americans, suburban women and millennials — that he said has on the whole been turning out in strong numbers in battleground states where there is early voting.

Mook said the campaign is confident that its early-voting totals will amount to a “firewall” on Election Day, or, as he described it, “a lead that Donald Trump is incapable of overcoming.”

He cited several states where Clinton stands to benefit from the strong early-voting turnout, particularly among Latinos, including Florida, Nevada and North Carolina.

In Michigan on Friday, Clinton made a pitch aimed at boosting African American turnout in a state where her advisers have suggested Trump could be doing better, given its manufacturing losses and large population of ­working-class whites, Trump’s strongest constituency.

At a rally in Detroit, Clinton talked about issues including criminal justice reform, college affordability and systemic racism, all of which are of particular importance to black voters. She also criticized Trump for portraying the lives of black people as being “all about crime and poverty and despair.”

“We’re doing everything we can to make sure that we get the numbers that we need,” Clinton’s campaign chairman, John Podesta, told reporters earlier Friday. “Michigan is a state that we feel like we’ve got a lead, and we want to make sure that we hold that lead.

“We want to make sure that we get the vote out and make sure people are enthusiastic. We want to end with a crescendo of enthusiasm,” he said.

The Clinton campaign also began airing television ads in Michigan for the first time in the general election this week.

Trump will make one last swing through two Western battleground states: Colorado and Nevada. He also plans to campaign in Iowa, a state where he has performed consistently well in the polls in recent months.

And Trump is slated to hold his final event before Election Day on Monday night in New Hampshire, the state where he notched his first primary win.

Polls have shown Clinton leading in New Hampshire for a long time, but recent surveys signal a turn in Trump’s direction. New Hampshire’s many white ­working-class voters — as well as its independent streak — make it a volatile place where Republicans hope voters will break late toward Trump.

Clinton’s schedule is being driven in part by a desire to make stops in states that have not had early voting, in hopes of providing a burst of momentum ahead of Tuesday.

The schedule of Clinton’s running mate, Sen. Tim Kaine of Virginia, illustrates the campaign’s dual focus on trying to protect leads as well as contest close states.

On Monday, Kaine is to return to his home town of Richmond to rally voters in Virginia, a state where Clinton’s lead has dwindled in recent weeks.

The plans of the two tickets also highlight a Democratic advantage that will be on full display in coming days: a much stronger and deeper bench of surrogates that can fan out across the country.

Besides Clinton and her running mate, the Democrats are also dispatching a sitting president, a former president, a sitting vice president, a popular first lady and Clinton’s former primary rival, Sen. Bernie Sanders of Vermont.

Obama campaigned on Clinton’s behalf Friday at two rallies in North Carolina, a state that could go either way on Tuesday and where early-voting participation has lagged among African Americans, a key part of the president’s coalition in 2008 and 2012.

And on Monday, a full slate of Democratic stars plans to join forces in Philadelphia for a final push of Clinton’s candidacy. Joining her, the campaign says, will be Obama, first lady Michelle Obama, and Bill and Chelsea Clinton.

Wagner reported from Washington. Jenna Johnson in Wilmington, Ohio, and James Hohmann in Selma, N.C., contributed to this report.