5 Stories You'll Care About in Politics This Week

— -- The campaign finally found a steady, mid-summer rhythm last week, as Donald Trump found himself atop the GOP polls and found a friend in Ted Cruz. The big story wasn't political, but that could change: President Obama's landmark nuclear deal with Iran made foreign-policy headlines, and this week we'll find out how it's playing back home.

Here's a glimpse at some of the stories the ABC News political team will be tracking in the week ahead:

SELLING THE IRAN DEAL

Obama's negotiators secured what's appropriately been called a major legacy achievement, and a visibly emboldened president now faces the challenge of selling it to a skeptical Congress, which will have 60 days to review the deal. Obama's opponents will need a supermajority to block it, but Obama has flirted with veto-proof levels of opposition to the Iran negotiations before. On Thursday, John Kerry and Energy Secretary Ernest Moniz will testify before the Senate Foreign Relations Committee, culminating a years-long effort to sell an Iran rapprochement on the Hill.

...AND GETTING CLOSER TO CUBA.

A common refrain from GOP presidential candidates, Jeb Bush chief among them, is that Obama has improved U.S. relations with only two countries: Iran and Cuba. This week will also see the next step in Obama's warmer relations with the latter, as both U.S. and Cuban “interest sections” — lesser diplomatic posts — will officially become embassies in Havana and DC, while Kerry will host Cuba's foreign minister at the State Department. The Obama administration is making this move quietly, but expect to hear loud complaints from Republicans on the trail.

THE 2016 FIELD IS SET (MOSTLY).

Except for former Virginia Gov. Jim Gilmore, who's expected to announce his candidacy in early August, the 2016 presidential field will finally be set next week, when Ohio Gov. John Kasich jumps in the race. He's expected to do that at his alma mater, Ohio State University, Monday evening. Kasich will bring the field of GOP candidates to 16; he's the last possible contender we expect to announce. And it can't come soon enough, as the first GOP debate will be hosted by Fox on Aug. 6.

CAN TRUMP STAY ON TOP?

So far, The Donald has successfully morphed from a real-estate mogul/reality-TV star into a leading presidential primary contender. In the last major national poll, released by Fox News on Thursday, Donald Trump again led the GOP field. Can it last? At this point, there's little reason to believe it can't. In the latest ABC News/Washington Post survey, Trump was extremely unpopular nationally, but since his announcement and controversial comments about Mexican immigrants, his favorable ratings had shot up to 57 percent among Republicans — suggesting the controversy has, if anything, galvanized support for him in the primary. Unless something else changes, Trump figures to keep riding the wave of media attention.

A MORE OPEN CLINTON CAMPAIGN?

After reporters mocked the Clinton team for dragging them behind a rope at a July 4th parade, the campaign let Hillary loose in a less-controlled setting this week, allowing audience members to challenge her on climate policy at a town-hall in New Hampshire and letting reporters ask more questions at a post-event session. It was a fuller departure from the earlier phase of the campaign, in which Clinton met with small groups and restricted press access to her house parties. We'll find out over the course of the week whether there's been a turning point in Clinton's press strategy.

This story has been corrected. John Kasich will be the 16th Republican presidential candidate, not the 15th.