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

200 days in, Trump has failed to unite the GOP

WASHINGTON — Every new president has the golden opportunity to unite his political party, especially when that party has been out of the White House for eight years. But six and a half months into Donald Trump's time in office, the Republican Party seems as divided as it was a year ago, right before Trump's nomination. For example:

Three Senate Republicans voted to effectively stop (at least for now) the GOP efforts to repeal and replace Obamacare;

Another GOP senator, Jeff Flake of Arizona, has a new book that criticizes President Trump and his party (“I am concerned at the direction the party is going — protectionism in particular, kind of an anti-immigrant fervor,” Flake said on “Meet the Press” yesterday);

Congressional Republicans disagree on whether the debt ceiling should be raised with or without accompanying spending cuts;

Republicans overwhelmingly voted for a Russia sanctions package, forcing President Trump to sign it over his own objections;

GOP senators sided with Attorney General Jeff Sessions after the president attacked Sessions as “beleaguered”;

And prominent Republicans are already jockeying for 2020, sensing a weakened Trump, the New York Times wrote over the weekend (“They see weakness in this president,” Sen. John McCain, R-Ariz., said).

Of course, the GOP divisions in 2016 didn't stop Trump from winning the presidency; in the end, the Republican Party and its voters joined hands to defeat Hillary Clinton. But less than seven months into his presidency, Trump’s biggest missed opportunity during this honeymoon phase very well might be his inability to unite his own party, especially inside Congress.

“It’s partly because they have this Republican president who is not really a Republican and not really a conservative,” NBC’s Andrea Mitchell observed on “Meet the Press” yesterday.

Trump took to Twitter Monday morning to argue that his base is bigger and stronger than ever.

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“The Trump base is far bigger & stronger than ever before (despite some phony Fake News polling). Look at rallies in Penn, Iowa, Ohio,” he tweeted.

“The fact is the Fake News Russian collusion story, record Stock Market, border security, military strength, jobs..... Supreme Court pick, economic enthusiasm, deregulation & so much more have driven the Trump base even closer together. Will never change!”

But if Republicans are truly united, then why have they struck out (so far) on health care? Why are they at odds over what to do about the debt ceiling? And why are prominent GOP senators already publishing books criticizing their own president? After all, there’s a difference between Trump’s base and the Republican Party.

A defensive Pence fires back at New York Times piece suggesting he’s eyeing 2020

As mentioned above, the New York Times wrote over the weekend that several Republicans — including Vice President Pence — are already eyeing 2020.

“Though it is customary for vice presidents to keep a full political calendar, [Pence] has gone a step further, creating an independent power base, cementing his status as Mr. Trump’s heir apparent and promoting himself as the main conduit between the Republican donor class and the administration.

"The vice president created his own political fund-raising committee, Great America Committee, shrugging off warnings from some high-profile Republicans that it would create speculation about his intentions.”

But on Sunday, Pence took the extraordinary step in releasing a statement responding to the New York Times.

“Today's article in the New York Times is disgraceful and offensive to me, my family, and our entire team,” he said in the statement. “The allegations in this article are categorically false and represent just the latest attempt by the media to divide this Administration.”

More: “Whatever fake news may come our way, my entire team will continue to focus all our efforts to advance the President's agenda and see him re-elected in 2020. Any suggestion otherwise is both laughable and absurd.”

Where the GOP is falling short under Trump, according to Sen. Jeff Flake

“Meet the Press” on Sunday took an in-depth look at America’s broken politics — and broken political parties.

Here’s where the GOP is falling short, according to Sen. Flake: "[M]y concern is that populism is a sugar high and once you come off it, it’s particularly troublesome for the party,” he told one of us yesterday.

More: “I wish that we, as a party, would have stood up, for example, when the birtherism thing was going along. A lot of people did stand up but not enough.” And: “[D]uring rallies when the chants, ‘Lock her up,’ you know, we shouldn't be the party for jailing your political opponents. And anybody at that rally, anybody at those rallies, ought to stand up and say, ‘That's inappropriate. We shouldn't be doing that.’”

Where the Democratic Party is failing short, per Gov. Jerry Brown

And here’s what California Gov. Jerry Brown said about his Democratic Party on “Meet” yesterday: “Democrats have been the champion of working people, and they haven't been able to deliver in face of these global trends. And, yes, you'd have to say that leadership has not been clever enough, or strong enough, or perhaps visionary enough.”

Brown added, “[I]t takes values, believing in right and wrong and a sense of what America's all about. And it takes a certain vision, how the hell do we get out of this? And it takes some political skill at the same time. All three of those things.”

Tillerson: U.N. sanctions prove world is united against North Korea’s missile tests

“Imposing tough sanctions against North Korea shows that the world is united in condemning the regime's recent missile tests, Secretary of State Rex Tillerson said Sunday,” per NBC’s Abigail Williams and Phil Helsel.

“Tillerson made the comments during a trip to the Philippines, a day after the United Nations Security Council unanimously approved sanctions against the isolated regime. ‘The best signal that North Korea could give us that they’re prepared to talk would be to stop these missile launches,’ Tillerson told reporters in the Philippine capital of Manila. ‘We've not had an extended period of time where they have not taken some type of provocative action by launching ballistic missiles.’”

Bernie Sanders supporters go after Kamala Harris

Speaking of divided political parties, check out this Washington Free Beacon article: “Progressive Democrats have not embraced rising star Sen. Kamala Harris (D, Calif.), highlighting a rift within the Democratic Party that evidently did not end with the 2016 Democratic presidential primary... Nomiki Konst, a Sanders supporter who serves on the Democratic National Committee's Unity Commission, told potential Harris supporters that they should ‘follow the money.’ ‘The Democrats will not win until they address income inequality, no matter how they dress up their next candidate,’ Konst said. ‘If that candidate is in bed with Wall Street, you may as well lay a tombstone out for the Democratic Party now. Voters are smart; they can follow the money.’”

Now it’s notable that Sanders and Harris — themselves — aren’t sparring. But it’s also clear that some elements of the left want to continue the fights of 2016, with Kamala Harris as the proxy for Hillary Clinton.