When most of the rest of the 2016 Republican presidential field issued fiery statements denouncing the Iran nuclear agreement, Kentucky Sen. Rand Paul, R-Ky., remained silent. Late Tuesday afternoon, Paul broke that silence by coming out against the deal.

"The proposed agreement with Iran is unacceptable and I will vote against the agreement," he wrote on Twitter, objecting that "sanctions relief precedes evidence of compliance" and "Iran is left with significant nuclear capacity."

Instead Paul prefers keeping "the interim agreement in place," suggesting he would be open to continuing negotiations over Iran's nuclear program.

The Kentucky senator has been a wildcard throughout the Iran talks. He opposed additional sanctions while the negotiations were ongoing, one of only two Republicans in the Senate who declined to support a bill that would impose them. He has said, "I am in favor of negotiations over war and I think I've been one of the reasonable people in our party who has not been beating the drums for war."

But Paul also signed a letter prepared by Sen. Tom Cotton, R-Ark., pointing out that the executive agreement wasn't a binding treaty. He also voted for the Corker-Menendez legislation that subjected the deal to congressional review.

Paul tried to triangulate between the president and Iran hawks in his own party when he formally launched his presidential campaign in April. "The difference between President Obama and myself — he seems to think you can negotiate from a position of weakness," he said. "Yet, everyone needs to realize that negotiations are not inherently bad, that trust but verify is required in any negotiation but that our goal always should be and always is peace not war!"

This removes the Iran deal as an issue where the rest of the Republican presidential field piles on Paul, but some of his father's supporters have found him too hawkish on Tehran, especially after he signed the Cotton letter.