As the weather heated up this summer, so did caucus season in Iowa. A slew of candidates have been traveling across the state to pitch their message to voters ahead of February’s Iowa Caucus, while state officials have also made headlines.

Here is a rundown of a few big stories, from Iowa and nationally, that made waves in politics this summer:

Donald Trump

By all calculations, Trump has defied the laws of politics while often raising eyebrows with the controversial statements he makes, but his poll numbers have skyrocketed in the months following his May announcement he would run.

“He’s really tapped into the [conservative] version of populism,” said Mack Shelley, professor of political science. “It’s kind of a good trick for someone to say he’s worth $10 billion to be able to attract support from those who are far down on the income schedule.”

Trump has been somewhat vague on specific policy, but he did release a six-page policy paper related to immigration — a topic that has caused controversy due to his comments on the subject.

As for the populist appeal, Trump said he supports “free trade,” but has been skeptical on trade deals that could hurt American workers. He has repeatedly called U.S. officials “stupid” and “incompetent” for their handling of trade. Trump has also said, with his massive wealth, he can self-fund a campaign and will not be beholden to special interests.

A poll conducted last week by CNN/ORC, which polled voters nationally, showed Trump at 22 percent support. His closest competitor was retired neurosurgeon Ben Carson — also a political outsider — at 10 percent. He also leads in the most recent Iowa polls.

Hillary vs. Bernie

While Democratic frontrunner Hillary Clinton still maintains a wide lead in most polling, Vermont Sen. Bernie Sanders, the independent, self-described “socialist,” has been gaining ground and drawing huge crowds at his events.

Sanders drew upwards of 30,000 people to an event in Portland, Ore. as recently as Aug. 10. In comparison, the largest crowd size Clinton garnered was at her New York launch, which drew about 5,000 people.

Clinton continues to face questions about her use of a private email server as Secretary of State. Some Democrats worry the issue continues to paint Clinton as untrustworthy, and that may open the door for more candidates to jump in the Democratic side.

In Iowa, a CNN/ORC poll of likely caucus voters earlier this month showed Clinton at 51 percent with Sanders at 31 percent.

Biden 2016?

While Clinton has continued to face questions on her trustworthiness numbers and continues to face ongoing scrutiny about her email server, there has been chatter on the left about Vice President Joe Biden jumping in the race.

Several news outlets, including The New York Times, The Wall Street Journal and Politico, have all cited sources saying Biden has been spending time talking to his closest advisors about a potential run in 2016. CNN also reported Saturday that Biden met with Massachusetts Sen. Elizabeth Warren — a favorite among progressive Democrats.

While he has not officially made any announcement, Biden did make a trip to Iowa earlier this year, visiting Drake University in Des Moines in February.

“[Clinton] still has a healthy lead, but she could have some support siphoned off from Biden and Sanders,” Shelley said. “One of them could conceivably eclipse her at some point.”

Former Vice President Al Gore and Secretary of State John Kerry have also been floated as potential candidates that may join the Democratic nomination contest.

Some candidates struggling

While Republicans like Former HP CEO Carly Fiorina and Ohio Gov. John Kasich have seen recent spikes in polling, at least two Republicans have seen a disappointing summer when it comes to polling and campaigns.

Kentucky Sen. Rand Paul, who began the summer polling in the double digits in Iowa, has seen a sharp drop off, now typically only coming in with about a few percentage points.

Former Texas Gov. Rick Perry has also consistently polled at just a few percentage points despite many trips to Iowa. Several news outlets reported earlier this month that Perry had stopped paying staffers — a sign fundraising dollars to his campaign have dried up.

“Perry doesn’t seem to have caught fire this time around. He certainty has not been able to tap into the really deep pocketed supporters,” Shelley said. “He doesn’t seem to have a distinctly identifiable niche [policy wise].”

Besides Sanders, several Democrats are also struggling to make any ground in polls against frontrunner Clinton. Former Maryland Gov. Martin O’Malley is averaging 4 percent support in Iowa polling, even after dozens of stops in the state. Former Virginia Sen. Jim Webb and former Rhode Island Gov. Lincoln Chafee both poll around 1 percent.

Iran Nuclear Deal

Perhaps the biggest policy story of the summer came when news of an agreement between Iran and five other powers had been reached regarding Iran’s capabilities when it comes to building a nuclear weapon.

President Obama and Secretary of State Kerry have been making the rounds on television and to members of Congress to lobby them to support the deal. Congress has a say when it comes to lifting economic sanctions on Iran, but even if Congress votes down the removal, Obama will veto. It would take two-thirds support in each chamber for keeping sanctions for Congress to override the veto.

All five Republicans in Iowa’s delegation are likely to oppose the deal. Some have said they are continuing to review it, while some have already announced opposition.

“I have very serious concerns that this agreement concedes too much to Iran and will ultimately strengthen the pathway for Iran to achieve a nuclear weapon,” said U.S. Sen. Joni Ernst.

U.S. Rep. Dave Loebsack, the only Democrat in Iowa’s delegation, has yet to announce his support or opposition.

“Republicans for the most part will be able to use this as a political football [throughout caucus season],” Shelley said.

King gets a challenger, Loebsack likely safe

U.S. Rep. Steve King of Iowa’s fourth district was able to beat his 2014 opponent by a huge 23.3 percent margin, but that has not stopped O’Brien County Democratic Party chair Kim Weaver from jumping in the race.

At the Iowa Democrat’s annual “Wing Ding” dinner, Weaver announced she plans to challenge King. She offered a wide range of issues to those in attendance, taking a fairly liberal stance on every issue.

In Iowa’s second district, Loebsack still kept his seat by just over 5 percent in the 2014 midterms that saw a Republican wave. Loebsack has yet to get any official challengers for 2016, but his seat leans Democratic and should be an easy save, Shelley said.

First and third District races coming together, will be close

First-term U.S. Reps. Rod Blum and David Young both have several Democrats hoping to take over their seats, and both races are listed as “toss-up” seats by several news outlets that rate each district every election.

In Iowa’s first district, Blum narrowly defeated former House Speaker Pat Murphy by just 2.3 percent. Murphy has jumped in the race again this cycle, while Cedar Rapids Councilwoman Monica Vernon and former Saturday Night Live star Gary Kroeger are seeking the Democratic nomination.

In Iowa’s third district, Young defeated former state Rep. Staci Appel by a wider margin — 10.5 percent — but a presidential election year will be closer. Iraq war vet and 2014 House candidate from Iowa’s 4th district, Jim Mowrer, has announced he will seek the seat. Des Moines businessman Desmund Adams has also announced his intention to run.

Shelley said it looks like Blum’s district, which voted for Obama by double digits in 2012, is more likely to flip, because of the constituency in the first district.

Three Democrats challenging relatively safe Grassley

At least three Democrats have stepped up to challenge one of Iowa’s most popular politicians — longtime U.S. Sen. Chuck Grassley.

Attorney Tom Fiegen and former State Rep. Bob Krause are officially seeking the Democratic nomination. State Sen. Rob Hogg of Cedar Rapids has formed an exploratory committee for a possible run.

“Like many Iowans, I believe we need Congress to work better for all of our citizens and our country’s future,” Hogg said. “In order to get Congress to work better, Iowans know it will require new leadership.”

Grassley has kept campaigning on the down low during the spring and summer, but has held some fundraising events throughout the state.

“This is about as safe of a Republican seat as you’re going to find,” Shelley said. “He’s very popular within the state and is a major player in the Senate. It would be almost impossible for a Democrat to win that election unless something major does happen.”

Several other stories made headlines across the state, including Gov. Terry Branstad’s veto of one-time funding for state schools and a plan to reopen state mental health facilities. Also, Republicans in the statehouse chose new leadership following the announcement that Speaker Kraig Paulsen would resign his speakership and not seek reelection.