Following President Donald Trump’s announced withdrawal from the 2015 Iran nuclear deal, GOP Sen. Dean Heller signaled his support and for the second time in two weeks attacked his likely opponent in November, Democratic Rep. Jacky Rosen, for supporting the deal.

“Nevadans deserve better than Jacky Rosen’s murky and weak stance on this evil regime,” Heller campaign spokesman Keith Schipper said in a release tweeted from Heller’s campaign account. “We need strong leadership against a nuclear Iran, something Rosen refuses to show.”

Heller’s campaign also reprised allegations that Rosen’s position on the deal—reached in 2015 to curb Iran’s nuclear weapons program—has changed, including during her 2016 campaign.

“Rosen thought President Obama made the best possible deal, but was against it just a month later,” the release said, adding that Rosen “has flirted with every position imaginable, and no matter what she says about the announcement today, chances are likely her tune will change eventually.”

Rosen’s campaign has denied the claim and argued that she has consistently called for robust enforcement of the deal, but has noted that had she been in Congress at the time, she would not have voted for it.

“Jacky Rosen has taken real bipartisan action to hold Iran accountable and support Israel as our most important ally in the Middle East. Nevada voters will have a choice in this race between Jacky's record of tough, smart solutions to keep America safe and Senator Heller's record of being a spineless rubber stamp for [Senate Majority Leader] Mitch McConnell and President Trump," Rosen campaign spokesman Stewart Boss said Tuesday, pointing to measures she’s supported as a member of the House Armed Services Committee.

The back-and-forth came after Heller initially tweeted a more innocuous comment embracing Trump’s decision.

“The Iran Deal was a sham and they must be held accountable,” Heller tweeted from his campaign account.

Heller’s attack is similar to the salvo he launched last week when he targeted Rosen, a Democrat, for supporting the deal. Then, he accused her of backing Iran and abandoning American ally Israel. Rosen’s campaign took offense and called for an apology because she is Jewish and has been an active member of Nevada’s Jewish community, including a stint as president of Congregation Ner Tamid in Henderson.

After Trump’s announcement, Heller’s congressional office released a statement in which he argued that the deal— also known as the Joint Comprehensive Plan of Action, or JCPOA—was flawed because it did not address ballistic missile tests or Iran’s support for the regime of Syrian President Bashar al-Assad.

“The Iran deal was never good for America or our friends in the Middle East. This agreement has done nothing to stop Iran from acquiring a nuclear weapon or promote peace – in fact, it has done just the opposite,” Heller said in a statement. “Iran has been emboldened since President Barack Obama signed the Joint Comprehensive Plan of Action three years ago. In the face of this agreement, Iran has conducted ballistic missile tests, harassed U.S. naval ships in the Middle East, and helped prop up the murderous Assad regime in Syria. Members of Iran’s parliament have shouted ‘death to America’ and its Supreme Leader Ayatollah Ali Khamenei has said ‘Israel will not exist in 25 years.’”

Heller’s statement contrasts with Rosen’s, where she opposed the president’s move to withdraw from the deal.

“As a Member of the House Armed Services Committee, I’ve heard from military and intelligence experts about the dangers of withdrawing from the JCPOA without evidence of a material breach,” Rosen said in a release. “After the JCPOA was agreed to, it should have been robustly enforced - not used as a political football. We need to hold Iran accountable in every way we can, and we cannot allow Iran to restart its nuclear program. Unfortunately, backing out of this agreement means undermining our international alliances, jeopardizing our national security, and re-opening Iran’s path to developing a nuclear weapon.”

Rep. Dina Titus, Rep. Ruben Kihuen and Sen. Catherine Cortez Masto also issued statements critical of the president’s decision.

Sen. John Thune of South Dakota, chairman of the Senate Republican Conference, a position in the GOP leadership, said he thinks it’s good politics to side with Trump against the deal.

“I think, at least at the moment, it’s probably helpful for a lot of our candidates to be adopting the president’s position because I think it’s the one that most Republican voters agree with,” Thune said.

Heller is running neck and neck with Rosen, according to a recent poll commissioned by The Nevada Independent, which underscores the importance of keeping Republican voters engaged so that they turnout to vote in the general election. Embracing Trump’s position helps in that effort.

However, Heller must be careful to not turn off moderate and independent voters who he also needs to win. The state’s moderates could be decisive and helped swing Nevada for Hillary Clinton in the 2016 presidential election.

Another example of a Republican using the Iran issue in a Senate campaign comes from Missouri, where the state’s attorney general, Josh Hawley, who is expected to face off against incumbent Sen. Claire McCaskill, sent out a release after Trump’s withdrawal, asking where she stood on the issue.

“We should be standing with President Trump and Israel today,” Hawley’s campaign said in a statement. “If you aren’t, you’re standing with the mullahs and [former Secretary of State and Iran deal author] John Kerry. Senator McCaskill needs to make it clear that she stands with President Trump and Israel and not the mullahs.”

But not all Republicans were in favor of leaving the deal. House Armed Services Committee chairman Mac Thornberry told Fox News Sunday that he “would counsel against” leaving the deal. “The key question is, ok, what happens next if the U.S. pulls out? Does Iran kick out those inspectors so we lose the visibility we have?”

Rep. Mike Turner of Ohio, who is chairman of the House Armed Services Committee’s Tactical Air and Land Forces Subcommittee, also voiced his concerns.

“The Iran Deal is a deeply flawed agreement,” Turner, who is also a member of the House Intelligence Committee and chairman of the U.S. Delegation to the NATO Parliamentary Assembly, said in a release. “However, without proof that Iran is in violation of the agreement, it is a mistake to fully withdraw from this deal. Now, we need to work with our allies to fix this flawed agreement to ensure the world is not facing a nuclear Iran.”

Sen. Chris Van Hollen of Maryland, chairman of the Democratic Senatorial Campaign Committee, which focuses on electing Democrats to the Senate, said that leaving the deal is bad policy and voters know that.

“I think the American people do not want another war in the Middle East,” Van Hollen said. “This agreement would cut off the different paths for Iran to obtain a nuclear weapon and [the White House and Republicans] have provided no alternative plan.”

He believes that the decision to leave the deal raises concerns about the U.S. honoring agreements ahead of upcoming denuclearization negotiations with North Korea and is an effort to undo the achievements by former President Barack Obama.

“The message this sends is you can’t trust the United States to keep its word,” Van Hollen said, adding that “this seems to be more aimed at President Obama than protecting our national security.”