Democratic Party frontrunner Hillary Clinton gave her support to a new nuclear agreement worked out with Iran by the United States and five other Western nations, standing with President Obama and against Republicans who voiced immediate suspicions about the deal.

"This is an important step in putting the lid on Iran's nuclear program," Clinton said after meeting with House Democrats.

"The President called me late last night to tell me that an agreement had been reached," the former Secretary of State told reporters.

Clinton's trip to Capitol Hill was originally intended to highlight an economic agenda that she laid out in a speech on Monday in New York, but events swiftly overtook that, as she spoke with lawmakers in both the House and Senate about the Iran agreement.

Democratic Senators emerged from a lunch meeting with Clinton saying that she had helped frame the rationale behind the agreement with Iran.

"She gave great context to how we go to this point," said Sen. Clare McCaskill (D-MO), "going through in some detail, how hard it was to get everyone on the sanctions regime."

"It was important for her to remind everyone, that didn't happen by magic, it took a lot of shuttle diplomacy," said Sen. Tim Kaine (D-VA), who said Clinton clearly had played an early role as Secretary of State.

Overall, reaction to the deal broke along party lines, with Republicans skeptical, and many Democrats ready to accept a diplomatic solution.

Democrats were more forgiving.

"I applaud President Obama’s leadership and commitment to peace and diplomacy," said Rep. John Lewis (D-GA).

"This Iran deal gives Ayatollah Khamenei exactly what he wants: billions of dollars in sanctions relief, validation of the Iranian nuclear program, and the ability to stymie inspections," said Rep. Ron DeSantis (R-FL).

The White House has several days to submit the agreement to the Congress, which will then have just over two months to review and vote on a resolution of disapproval.

President Obama says he will veto any disapproval resolution that reaches his desk; it means the Congress would need a two-thirds supermajority in both the House and Senate to stop this Iran agreement.

Late on Tuesday night, Hillary Clinton's campaign emailed the following statement in support of the Iranian nuclear deal:

"In light of the international community's long history and experience with Iranian behavior, the highest priority must be given to effective enforcement of the agreement.  Signing is just the beginning.  As President, I would use every tool in our arsenal to compel rigorous Iranian compliance.  At the outset, we must see the verified roll back of the Iranian nuclear program required by the agreement.  We can never permit Iran to evade its obligations or to place any suspicious site off limits to inspectors.  And the response to any cheating must be immediate and decisive – starting with the return of sanctions but taking no options off the table, including, if necessary, our military options.

"The message to Iran should be loud and clear:  We will never allow you to acquire a nuclear weapon; not just during the term of this agreement – never.

"Today's agreement is the culmination of a sustained strategy of pressure and engagement executed over many years.  As Secretary of State, I logged tens of thousands of miles and twisted a lot of arms to build a global coalition to impose the most crippling sanctions in history. That unprecedented pressure delivered a blow to Iran's economy and gave us leverage at the negotiating table, starting in Oman in 2012.  I know from experience what it took to build a global effort to get this done; I know what it will take to rally our partners to enforce it. 

"Going forward, we have to be clear-eyed when it comes to the broader threat Iran represents.  Even with a nuclear agreement, Iran poses a real challenge to the United States and our partners and a grave threat to our ally Israel. It continues to destabilize countries from Yemen to Lebanon, while exacerbating the conflict in Syria. It is developing missiles that can strike every country in the Middle East. And it fuels terrorism throughout the region and beyond, including through direct support to Hamas and Hizballah.  We have to broadly confront and raise the costs for Iran's destabilizing activities, insist on the return of U.S. citizens being held in Iranian prisons, and strengthen security cooperation with our allies and partners. Sanctions for terrorism, and other non-nuclear sanctions, must remain a key part of our strategy and must be vigorously enforced.

"Israel has to be confident that the United States will always ensure its Qualitative Military Edge in the region and its capacity to defend itself by itself.  As President, I would invite the senior Israeli leadership to Washington for early talks on further strengthening our alliance.  We must also deepen our security relationship with our Arab partners threatened by Iran. This includes our continued presence and providing needed capabilities.  Iran should have no doubt about our support for the security of our partners.

"I know that there are people of good faith who oppose this deal - people I respect. They raise concerns that have to be taken seriously.  They are right to call for extreme vigilance.  I am as familiar with Iranian behavior and the need to confront it as anyone.  I support this agreement because I believe it is the most effective path of all the alternatives available to the U.S. and our partners to prevent Iran from acquiring a nuclear weapon.  

So we should applaud President Obama, Secretary Kerry, and Secretary Moniz for getting this done, and proceed with wisdom and strength in enforcing this deal to the fullest and in meeting the broader Iranian challenge."