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

The GOP’s health care effort is unraveling

You know things aren’t going well at the White House when the president would rather want to talk about his taxes than health care. And that brings us to what is still the biggest story American politics: The Republican’s health care overhaul efforts are unraveling. Consider all of the recent developments:

Conservatives don’t think the House GOP plan goes far enough. "After reviewing this legislation and receiving the Congressional Budget Office score today, it is clear that this bill is not consistent with the repeal and replace principles for which I stand,” Rep. Rob Wittman (R-VA) said.

Congressional moderates think it goes too far. “I plan to vote NO on the current #AHCA bill. As written the plan leaves too many from my #SoFla district uninsured,” Rep. Ileana Ros-Lehtinen (R-FL) tweeted yesterday.

The Congressional Budget Office projects 14 million fewer Americans won’t have health insurance by 2018 under the plan, and 24 million won’t have it by 2026.

Sen. Ted Cruz (R-TX) says the House bill won’t pass the Senate. “I have serious concerns about the current draft of the House bill,” he said, per the Washington Post. “As written, I do not believe the House bill would pass the Senate.”

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Sen. Tom Cotton (R-AR) is telling House Republicans not to vote for it. “I would say to my friends in the House of Representatives with whom I serve, ‘Do not walk the plank and vote for a bill that cannot pass the Senate and then have to face the consequences of that vote,’” he said.

A new Kaiser Health Tracking Poll shows more Americans have a positive view of the current Affordable Care Act (49%) than a negative view (44%), and a slight majority of respondents are opposed to repealing the law (51%).

And Newsmax’s Chris Ruddy, a close friend and confidante to Trump, is calling for “an upgraded Medicaid system to become the country’s blanket insurer for the uninsured” — something that Sen. Bernie Sanders (I-VT) would probably embrace.

Add them all up, and President Trump and House Speaker Paul Ryan have a big problem on their hands. There’s a reason why the White House is now falling back on the argument that if the House GOP plan doesn’t pass, repealing and replacing Obamacare might never happen.

"This is it,” White House Press Secretary Sean Spicer said yesterday. “If we don't get this through, the goal of repealing Obamacare and instituting a system that will be patient centered will be unbelievably difficult.”

Who leaked Trump’s tax return — and why?

Here’s the news on President Trump’s tax return that MSNBC’s Rachel Maddow broke last night: “The White House confirmed Tuesday night that President Donald Trump paid $38 million in federal income tax on more than $150 million in income for 2005 after MSNBC's ‘The Rachel Maddow Show’ said it would release the details. DCReport.org obtained two pages from what it said were Trump's 2005 Form 1040. The site's founder, David Cay Johnston, a former reporter for The New York Times, disclosed the details of the two pages, which he said were sent to him through the U.S. Postal Service, on Maddow's program... The White House said the $152 million in income was derived after accounting for ‘a large-scale depreciation.’ The pages show a writedown of $103.2 million. He paid the Alternative Minimum Tax of about $38 million.

But to us, the biggest news is: Who leaked these taxes to David Cay Johnston. And why? As NBC’s Ari Melber pointed out on “Today” this morning, only these people would have access to the tax return -- Trump, his family, his accountant, or the IRS. Melber also noted that it is NOT illegal for an individual to release his or her own taxes to the public. This morning, Trump tweeted, “Does anybody really believe that a reporter, who nobody ever heard of, ‘went to his mailbox’ and found my tax returns? @NBCNews FAKE NEWS!” But our question: How is it fake when the White House confirmed the numbers?

Put up or shut up time on any Trump-Russia investigation?

“Sen. Sheldon Whitehouse said Tuesday that FBI Director James Comey promised to tell him Wednesday whether the FBI is investigating ties between Russia and the campaign of President Donald Trump,” CNN reported yesterday. “The Rhode Island Democrat said that Comey made the promise in a March 2 meeting with him and Sen. Lindsey Graham, a Republican from South Carolina.” Per NBC’s Kasie Hunt, we already knew about this deadline. But it’s unclear if we’ll get any announcement from Comey today. As Graham noted on MSNBC’s “Morning Joe” this morning, per MSNBC’s Shirley Zilberstein:

MIKA BRZEZINSKI : Great to have on the show today, thank you. Big announcement today.LINDSEY GRAHAM: Well, yes. I hope. Well, there's a little be of confusion here. Senator Whitehouse and myself met with Director Comey, who I like, two weeks ago and said, "We're going to have hearing on Russia and I need to know if there's a criminal investigation regarding the Trump campaign or anything about Russia because I don't want to interfere with it so, I don't want to go blindly down the congressional path. If there's a criminal investigation, you need to inform Congress cause we're going to look into all things Russia and I gave him until today to let me know and I haven't heard yet.BRZEZINSKI: Okay, so he was very --GRAHAM: So, Senator Whitehouse's statement was I think a bit misconstrued. He did NOT promise us. We said we want to know by the 15th

How Big Data broke American politics

Over the last few months, we’ve been mulling over a theory: How did our politics get so polarized so quickly -- both in the campaigns that candidates run, and in the halls of Congress? We think there’s a lot of evidence that points to the Big Data revolution as the primary culprit. Why? In a bygone era, political pros started each campaign with the assumption that most elections are decided by persuadable voters in the middle, and each side set out to court those voters. But with the advent of massive amounts of voter data and the technological tools to harness it, campaign strategists realized that it was far easier — and cheaper — to try to out-mobilize their opponent by firing up their base and building a partisan firewall. And we see the consequences of that strategy reflected in a polarized electorate and in a government where ideological overlap has nearly ceased to exist. (An important note here: We’re not arguing that campaign data is WRONG. Actually, quite a lot of it was proven to be right in the last election. It’s just that it’s been misused in a way that’s bad for democracy.)

Here’s more, from our NBCNews.com piece outlining our theory of the problem, and how to fix it: "During and after elections, candidates and lawmakers have been increasingly incentivized — and enabled by Big Data — to cater to their bases to the exclusion of other voters. Political mapmakers and campaigners have discouraged the grey areas into nonexistence. But guess what? What Big Data can take away, it can also revolutionize. Imagine if all of these great technological tools were used to create more (small d) democratic competition into the people's House? If we want politicians to practice the art of politics again, then let's create an election system that encourages it by incentivizing candidates to court all available voters, not just their own partisans."

Trump’s Day

President Trump travels to Michigan, where he speaks at 2:20 pm ET… He then holds a “Make America Great Again” rally in Nashville, TN at 7:30 pm ET.

What were other presidents doing on March 15?