First Read is a morning briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

Why Trump can’t escape his ‘Birther’ past

On Thursday night, the Washington Post reported that Donald Trump refused -- again -- to say President Obama was born in the United States. “I’ll answer that question at the right time,” Trump said. “I just don’t want to answer it yet.” After Hillary Clinton seized on the issue before an audience of Latinos, a Trump campaign spokesman issued a statement saying that Obama WAS born in the U.S. “Having successfully obtained President Obama’s birth certificate when others could not, Mr. Trump believes that President Obama was born in the United States,” senior communications adviser Jason Miller said. And it’s possible that Trump tries to backtrack on his ‘Birther’ past at his campaign event in DC today. But there’s a big reason why he can’t escape it, no matter what he says: It’s a key part of his political identity. Indeed, just look at these Trump statements AFTER Obama produced his birth certificate in 2011:

An 'extremely credible source' has called my office and told me that @BarackObama's birth certificate is a fraud. — Donald J. Trump (@realDonaldTrump) August 6, 2012

When I was 18, people called me Donald Trump. When he was 18, @BarackObama was Barry Soweto. Weird. — Donald J. Trump (@realDonaldTrump) March 12, 2012

How amazing, the State Health Director who verified copies of Obama’s “birth certificate” died in plane crash today. All others lived — Donald J. Trump (@realDonaldTrump) December 12, 2013

Attention all hackers: You are hacking everything else so please hack Obama's college records (destroyed?) and check "place of birth" — Donald J. Trump (@realDonaldTrump) September 6, 2014

“Who knows [if Obama is a natural-born citizen]? Who knows? Who cares right now? We're talking about something else, OK? I'm going to have my own theory on Obama. Someday I'll write a book, I'll do another book that will do successfully.” -- Jan. 6, 2016

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So for Trump’s campaign -- or even Trump himself -- to backtrack on this ‘Birther’ past some 50 days before the election is like asking Hillary Clinton to backtrack on being married to Bill Clinton, or Bernie Sanders to backtrack on being a democratic socialist, or Barack Obama to backtrack on his fondness for Abraham Lincoln. It is part of Trump’s political identity, and his political following started with this.

It isn’t true to say Hillary Clinton or her ’08 campaign started the Birther movement

The other part of the Trump campaign statement from last night -- in fact, it was its beginning -- was pinning the Birther story on Hillary Clinton. "Hillary Clinton’s campaign first raised this issue to smear then-candidate Barack Obama in her very nasty, failed 2008 campaign for President. This type of vicious and conniving behavior is straight from the Clinton Playbook.” But that is untrue. While SUPPORTERS of Clinton stirred this conspiracy on the Internet, Clinton or her campaign NEVER said/suggested/insinuated that Obama wasn’t born in the United States. As the Washington Post wrote last year, “Clinton's campaign, one of the most thoroughly dissected in modern history, never raised questions about the future president's citizenship. The idea that it did is based largely on a series of disconnected actions by supporters of Clinton, mostly in the months between Obama's reaction to the Jeremiah Wright story and the Democratic National Convention.”

Why Team Trump addressing the Birther story doesn’t make much sense

The only way Trump addressing the Birther story makes sense is through the logic that “any day the campaign is about you is a good day.” Besides that, addressing it doesn’t make sense. Either he doubles down on his past statements, which only complicates the campaign trying to woo African Americans and to seize on the “Deplorables” controversy. Or he repudiates his past Birther statements, which raises the question if he has a political core. How can you beat the Birther drums for five years and then say you’re sorry 50-plus days before an election? If so, what does he believe? And what is he for? One other point here: With his poll numbers improving, Trump appears to be getting a little cocky (this, Dr. Oz, criticizing the African-American pastor). As we know, Hillary Clinton can sometimes be a terrible frontrunner. Maybe Trump isn’t a good one as well…

Clinton’s message problem: It’s not enough being against Trump

Speaking of Clinton, she’s had a message problem since mid-August: It isn’t enough being AGAINST Trump. She also to say what she’s FOR. Indeed, this was a problem that both Mitt Romney and John Kerry had, and look how their campaigns turned. That said, Clinton’s retooled stump speech yesterday started to get at the “for” issue. Some examples:

“But I want you, I want you to think with me for a minute about how I certainly feel lucky when I'm under the weather, I can afford to take a few days off. Millions of Americans can't. They either go to work sick or they lose a paycheck, don't they?”

“I'm running for the LGBT teenager here in North Carolina who sees your governor sign a bill legalizing discrimination and suddenly feels like a second-class citizen.”

“I've been involved in politics in one way or another for many years. It is not an easy business. It can get rough and I've built up some defenses. When it comes to public service, I'm better at the service part than the public part, but this is why I do it and this is who I'm in it for: to make life better for children and families. And that's what this race has always been about for me.”

Mr. Kasich Comes to Washington (to talk about supporting TPP)

Finally, guess who’s also in DC today? Answer: Ohio Gov. John Kasich, who is meeting with President Obama to discuss promoting the TPP trade agreement. “Friend, I will be in Washington, D.C. tomorrow to participate in a bipartisan discussion at the White House about the benefits of trade for job creation, innovation and improving national security,” he said in an email to his supporters. “Free trade is not only a powerful driver of job creation for Americans but it's also a national security issue. There's no better tool for America to encourage other nations to embrace freedom and equality than healthy trade relationships.”

On the trail

Hillary Clinton gives a speech in DC to the Black Women's Agenda Symposium … Donald Trump is also in DC, where he holds a campaign event at 10:00 am ET, and then he holds a rally in Miami, FL at 6:00 pm ET… And Michelle Obama stumps for Clinton in Fairfax, VA at 3:00 pm ET.

Countdown to first presidential debate: 10 days

Countdown to VP debate: 18 days

Countdown to second presidential debate: 23 days

Countdown to third presidential debate: 33 days

Countdown to Election Day: 53 days