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 a GOP rebellion against Trump is likely to fail

With the GOP convention now less than a month away, some Republicans are renewing their efforts to dump Trump. “Colorado delegate Kendal Unruh is the leader of the effort, which centers around changing the convention rules to include a ‘conscience clause’ that would allow delegates bound to Trump to vote against him, even on the first ballot at the July convention,” NBC’s Alex Jaffe reports. “A lot would need to happen for Unruh's efforts to prevent Trump from capturing the nomination. A majority of the 112-member Rules Committee would need to vote in favor of the change, and then enough of the convention's 2,472 delegates would need to invoke the ‘conscience clause’ to reject Trump.” But there’s one big reason why such an effort is likely to fail: It’s very difficult to beat SOMEBODY with NOBODY. Whom do these anti-Trump insurrectionists prefer to Trump? Ted Cruz? Marco Rubio (who looks he might run for his Senate seat)? House Speaker Paul Ryan, who has 100% ruled out a presidential bid? If you don’t have somebody to beat Trump, you’re unlikely to topple him at the convention.

The United States of Trump

There’s another reason why a GOP coup against Trump is likely to fail: The strength and depth of support of many of his primary voters, who aren’t your typical grand poobahs of the party. As NBC’s Benjy Sarlin writes in a richly reported analysis of Trump’s voters, many of them are Americans “alarmed by economic trends, unsure of their place in a more diverse nation and convinced that the major parties no longer have their interests in mind.” More: “According to our county analysis, one of the most dramatic predictors of [Trump’s] success early in the race was how much a county’s average pay had grown (or hadn’t grown) from 2004 to 2014. Another major predictor was the percentage of whites who participate in the labor force. Still another was whether residents were more or less likely to hold at least a high school degree.” And here’s Trump telling NBC’s Hallie Jackson why his GOP detractors can't stop him: He already beat them at the ballot box. “I worked for one year and we won all of those delegates. And, you know, I guess I'm at almost 1,600, 15-to-1,600… And I competed along with a lot of establishment people. I beat them all. And now a couple of them would like to come in through the back door. It's awfully hard when I win, what did I when, 37 or 38 states? So I win 38 states and somebody else won none, and they're going to be the nominee? I don't think so.”

Trump and GOP groups haven’t spent a dime on battleground-state ads

As Republicans -- once again -- plot to “stop Trump,” it’s worth pointing out that Hillary Clinton and Democrats are dominating the battleground-state airwaves. So far in June, Clinton and the outside groups backing her have spent a total of $23.4 million on ads in the battleground states of Colorado, Florida, Iowa, Nevada New Hampshire, North Carolina, Ohio and Virginia, according to ad-spending data from SMG Delta. By contrast, Republicans have spent $0 in these same eight states. That’s a 100 percent-to-0 percent advantage for Clinton and the Democrats in these battlegrounds. Here are the numbers in the battleground states for this month:

Priorities USA and Priorities USA Action (pro-Clinton outside groups): $15.9 million

Hillary for America: $7.5 million

All Trump/GOP presidential spending: $0

By comparison, in June of 2012, President Barack Obama and the outside groups supporting him had spent $45 million in ads in 11 battleground states, while Mitt Romney and his allies -- like Crossroads GPS and Americans for Prosperity -- spent $38 million. The biggest spenders back then for the month of June:

Obama for President: $38.5 million

Romney for President: $12 million

Crossroads GPS (anti-Obama group): $11 million

Restore Our Future PAC (Romney Super PAC): $6.6 million

Americans for Prosperity (anti-Obama group): $5.2 million

Priorities USA (pro-Obama Super PAC): $4.2 million

Price tag of Clinton’s battleground ad blitz is now at $20.9 million

Staying with the battleground-state ad spending, here are the updated market-by-market figures of Clinton’s buy (June thru July), which now stands at $20.9 million:

Ohio $5.2 million

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Cleveland-Akron, OH $1.6 million

Columbus, OH $1.0 million

Cincinnati, OH $1.0 million

Toledo, OH $645k

Dayton, OH $518k

Youngstown, OH $349k

Parkersburg, WV $52k

Wheeling, WV- Steubenville, OH $50k

Florida $5.1 million

Tampa-St Petersburg-Sarasota, FL $1.6 million

Jacksonville, FL $977k

West Palm Beach-Ft. Pierce, FL $890k

Ft. Myers-Naples, FL $882k

Mobile, AL-Pensacola, FL $498k

Panama City, FL $210k

Tallahassee, FL-Thomasville, GA $19k

North Carolina $3.7 million

Charlotte, NC $1.5 million

Raleigh-Durham, NC $895k

Greensboro-High Point-Winston Salem, NC $491k

Greenville-New Bern-Washington, NC $324k

Wilmington, NC $245k

Greenville-Spartanburg, SC-Asheville, NC $182k

Nevada $2.0 million

Las Vegas, NV $1.4 million

Reno, NV $547k

Virginia $1.8 million

Norfolk, VA $648k

Richmond-Petersburg, VA $591k

Roanoke-Lynchburg, VA $349k

Tri-Cities, TN-VA $86k

Harrisonburg, VA $74k

Charlottesville, VA $70k

Iowa $1.2 million

Des Moines-Ames, IA $568k

Cedar Rapids-Waterloo-Iowa City-Dubuque, IA $427k

Omaha, NE $155k

Ottumwa, IA-Kirksville, MO $37k

Colorado $1.1 million

Denver, CO $854k

Colorado Springs-Pueblo, CO $281k

New Hampshire $830k

Boston, MA $830k

Grand Total $20.9 million

Biden to blast Trump on foreign policy

At 1:30 pm ET, Vice President Biden will speak at the Center for New American Security’s annual conference, where he will blast Trump on foreign policy. The Los Angeles Times’ Memoli: “Biden’s address … opens as a defense of the Obama administration’s foreign policy record, one that has ‘positioned the United States at the forefront of tremendous opportunity,’ he will say, according to advance excerpts. But Biden will also target the presumptive Republican nominee, even if not by name, arguing that by turning inward, or seeking ‘sound-bite solutions in a world defined by complexity,’ the U.S. could “squander all of our hard-earned progress.’” More: “Biden’s speech Monday will highlight shared policy views and the party’s main argument against a President Trump: that he would put America’s standing in the world at risk. ‘We are at an inflection point — the choices we make today will direct the future of our world. And in this moment of uncertainty, the world needs steady American leadership more than ever,’ he will say. Biden will specifically target Trump’s praise for Vladimir Putin, arguing that embracing the president ‘at a time of renewed Russian aggression could call into question America’s long-standing commitment to a Europe whole, free and at peace.’”

Today’s gun measures in the Senate will all likely go down to defeat

“Spurred by the worst mass shooting in U.S. history, the Senate will vote Monday on a quartet of bills to prevent terrorists from buying weapons and overhaul the national background check system for firearms purchases. But the chamber’s big gun show on Monday is expected to be just that: political theater,” Politico writes. All four proposals are reheated versions of legislation the Senate rejected in the past. Despite a flurry of negotiations over the past week, and some movement among centrist Republicans toward a compromise that continued over the weekend, there’s little indication the outcome will be any different this time… The Senate will take a series of roll-call votes at 5:30 p.m. Monday.” Here’s NBC’s Luke Russert and Alex Moe with everything you need to know about today’s votes.

Bernie Sanders still has his Secret Service protection, which costs taxpayers $38,000 a day

The Washington Post: “Although Hillary Clinton has clinched the party’s nomination, Sanders retains one of the trappings of a top-notch candidate: A team of agents still guards him at his home, where they’ve constructed a small watch station on the property. They travel with him on commercial and charter flights and use a motorcade to whisk him through cities he visits. And they marched alongside him during a gay-pride event here in his home town after the Orlando shootings. Such round-the-clock protection can cost taxpayers more than $38,000 a day.” Folks, that means if Sanders takes his campaign all of the way up until the July 25 Democratic convention, the Secret Service could be more than $1.3 million.

On the trail

Hillary Clinton and Donald Trump are both in New York City, where they don’t have public events. Don’t forget to check out the political unit’s rolling minute-to-minute coverage of all the latest 2016 developments at the On the Trail liveblog at NBCNews.com.