THE TAKE with ABC News' Rick Klein

It turns out you don't have to wait for 2020 to see the intraparty squabbles in action. A not-so-quiet summer is exposing old rivalries and sparking new ones inside the Republican Party, raising questions about the viability of the fall agenda. There's Sen. Ron Johnson venting about Sen. John McCain's health care vote. There's prominent Trump donor Robert Mercer putting his money up to take out Sen. Jeff Flake. And now there's President Trump joining powerful allies in questioning the leadership of Senate Majority Leader Mitch McConnell. We've seen Trump turn on some of his most loyal lieutenants in the past. But something different happens when he puts senators in that position: They lose maneuverability, and they may lose political incentive to stay on the Trump train. This is not about mere words: Actual governing has to happen, and fast, in the fall. Until then the drift of the agenda is being felt acutely in the GOP donor world. "It is hard to go and make the case, give us the majority again,' when we haven't accomplished the things that we ran on," RNC Chairwoman Ronna McDaniel told us on the "Powerhouse Politics" podcast.

DANGEROUS AT THE TOP

Two of the most powerful Republicans in the country are on shaky ground, but for very different reasons. House Speaker Paul Ryan has, by most accounts, stood by the president as of late and is even now championing one of the president's prized promises: building that wall. But, the coming months may reveal some of the speaker's vulnerabilities as the House tries to pass a bill to raise the debt ceiling. Ryan used to be the torchbearer for fiscal conservatives, unflinching and unwilling to take on more debt without corresponding spending cuts. But this go-around, Ryan says he is with the White House. The administration wants less drama -- a clean deal with no strings attached. Could Ryan see a mutiny? On the other hand, Senate Majority Leader Mitch McConnell is taking the heat from the outside. The president showed once again that no one is off limits for @realDonaldTrump, when he blasted the leader personally for not getting a health care repeal done. Obviously, he cannot remove McConnell from his post, but it would be awfully hard to stay if he said McConnell should go, ABC News' MaryAlice Parks writes.

QUOTE OF THE DAY

"General Kelly and others on the [National Security Council] team were well aware of the tone of the statement of the president prior to delivery. The words were his own." --White House press secretary Sarah Sanders on Trump's "fire and fury" comment.

WHAT TO WATCH

ABC News' Chief Anchor George Stephanopoulos will sit down live with Anthony Scaramucci for his first interview since being fired from the White House, this Sunday on ABC News' "This Week."

NEED TO READ with ABC News' Daksha Sthipam

Trump could face GOP challengers in the 2020 election. As President Trump's approval among Republican voters drops, speculation looms about potential challengers from within the GOP ahead of the 2020 election. Some Republicans, including Vice President Mike Pence, are making moves -- such as meeting with donors -- that could be interpreted as signs of a 2020 run. http://abcn.ws/2vGbErS

RNC Chairwoman McDaniel: "We haven't accomplished the things that we ran on." Ronna Romney McDaniel, chairwoman of the Republican National Committee, said Republicans need to rack up some accomplishments to keep control of Congress on ABC's "Powerhouse Politics." "It is hard to go and make the case, give us the majority again,' when we haven't accomplished the things that we ran on," McDaniel said. http://abcn.ws/2usldqq

Suggestion McCain's tumor may have influenced health care vote "bizarre," spokesman says. Sen. John McCain's spokesman shut down a fellow senator's suggestion that the Arizona Republican's brain tumor may have affected his "no" vote on health care Wednesday. "It is bizarre and deeply unfortunate that Sen. [Ron] Johnson would question the judgment of a colleague and friend," McCain's spokesman told ABC News. http://abcn.ws/2ur4nfJ

Institute of Politics at Harvard Kennedy School announces fall 2017 fellows. Harvard IOP

Unarmed Russian Air Force jet overflies the Pentagon, Capitol, CIA. CNN

Top Trump donor ponies up to take out Flake. Politico

Ex-Sheriff Joe Arpaio says he isn't seeking Trump's pardon. Associated Press

The Note is a daily ABC News feature that highlights the key political moments of the day ahead. Please check back tomorrow for the latest.

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The Note: Republican progress grinds to halt with infighting at fever pitch - ABC News