President Barack Obama is blitzing senators and American voters prior to the Senate’s Tuesday vote on his still-secret plan for punishing the Syrian regime of Bashar al-Assad for firing nerve gas into rebel-held neighborhoods.

On Sunday evening, Obama dropped into a meeting held by Vice President Joe Biden with several swing-voting GOP senators, including Lindsey Graham of South Carolina, Susan Collins of Maine, Saxby Chambliss of Georgia, Bob Corker Tennessee, Kelly Ayotte of New Hampshire and Deb Fischer of Nebraska, according to the White House. Obama stayed for roughly 80 minutes.

On Monday, Obama will do face-to-face interviews with six networks, where reporters might prod him to outline the scope and limits of his planned aerial intervention into Syria’s civil war.

His deputies are also scheduled to make the case for action Monday and Tuesday. National Security Advisor Susan Rice, for example, will give a speech at the New America Foundation.

Vice President Joe Biden, however, is slated to visit Baltimore, where he is expected to tout a $10 million plan to dredge a deeper channel for ships.

On Tuesday, Obama will visit Democrats in the Senate before the critical vote, while his deputies will provide senators with last-minute classified briefings about who launched the nerve gas attack Aug. 21, one year after Obama declared such attacks would violate a “red line.”

On Tuesday evening, Obama is slated to give a national address in the face of polls that show broad public opposition to further involvement in Syria’s complex civil war.

Even if he wins a majority in the Senate, Obama will face an even more difficult task persuading Democratic and Republican legislators in the House to back his unknown plan.

The Syria war has reportedly killed 100,000 people. It was caused by sectarian, ethnic and ideological splits, and is being fueled by various outside rival powers, such as Iran, Russia, Turkey and Saudi Arabia.

The U.S. is already providing military aid to some rebels factions which fight alongside al-Qaida affiliates in a temporary alliance.

So far, however, there’s little reliable information about the scale and consequences of Obama’s planned red line aerial offensive.

That’s important, because legislators are concerned that any attack could help radical Muslim groups — including forces affiliated with the Muslim Brotherhood and al-Qaida — to seize control of Syria’s armory of chemical weapons for use against Israel, Europe and the United States.

Any takeover could also allow the Muslim groups to force millions of Arab Christians out of Syria, where they have lived for 2,000 years, some 600 years prior to the Muslim invasion in the 630s.

The scale and purpose of the planned aerial offensive is unclear.

ABC News reported that the operation is expected to inflict “more damage to Assad’s forces in 48 hours than the Syrian rebels have done

in nearly two years of civil war.” The plan, says ABC, includes strikes by 200 ship-launched Tomahawk missiles, plus a rain of bombs and missiles from heavily-lift B-52 and stealthy B-2 bombers.

The Los Angeles Times reported that Pentagon officials were planning a three-day barrage. “There will be several volleys and an assessment after each volley, but all within 72 hours and a clear indication when we are done,” said one officer, according to the Times. But the three-day strike “will not strategically impact the current situation in the war, which the Syrians have well in hand, though fighting could go on for another two years,” said another U.S. officer cited by the L.A. Times.

Obama’s chief of staff, Denis McDonough, decried concerns that the extensive strike would help al-Qaida affiliates topple Syria’s government, and then seize some of Syria’s large stores of chemical weapons.

“I am outraged for somebody to suggest that our people would be serving as allies to al-Qaida,” McDonough declared in a Sunday interview on ABC’s “This Week.”

That TV-ready anger was directed at GOP Texas Sen. Ted Cruz, who said last week that “young men and women sign up to join the military, not to, as you know, serve as al-Qaida’s air force.”

“We certainly don’t have a dog in the fight. …We should be focused on defending the United States of America,” Cruz told The Blaze.

McDonough, however, insisted that any strike would be big enough to ensure proper punishment to Assad for allowing the use of chemical weapons, even as he also suggested it would be small enough not to aid the al-Qaida affiliates, which comprise an important slice of the loosely-organized rebel armies.

The response will be a “targeted, consequential, limited attack against Assad forces and Assad capabilities so that he is deterred from carrying out these actions again. …This is a very concerned, concentrated, limited effort that we can carry out and that can underscore and secure our interests,” McDonough said.

He did not say how the U.S. would stop nearby al-Qaida forces from taking advantage of aerial attacks on Syria’s stretched military.

Rice is also expected to face a few tough questions from a generally favorable audience at the New America Foundation.

She may face questions about a Friday statement by America’s U.N. Ambassador Samantha Power that top White House officials had hoped that Syria’s use of chemical weapons would break the long-standing Syria-Iran alliance. “We thought perhaps a shared evidentiary base [of chemical attacks] could convince Russia or Iran — itself a victim of Saddam Hussein’s monstrous chemical weapons attacks in 1987-1988 — to cast loose a regime that was gassing it’s people,” Power told a progressive audience at the Center for American Progress on Sept. 6, according to a report in the Washington Examiner.

Iran is run by a Shia-style Muslim theocracy. Syria’s mostly secular dictatorial government is run by the minority Alawite clan, which also embraces a Shia-style version of Islam. This shared religion has cemented an alliance of the two countries, which are ringed by countries whose autocratic governments and laws are based on the rival Sunni variant of Islam.

Follow Neil on Twitter