As he has risen in the polls, Rubio has methodically sought to distance himself from the comprehensive immigration bill he coauthored more than two years ago. But Schumer, the veteran New York Democrat, is dragging him back into the fray, shining a spotlight on one of the 44-year-old's biggest vulnerabilities with the right as top Democrats seek to undermine the GOP senator's surging candidacy.
"He was not only totally committed -- he was in that room with us, four Democrats, four Republicans," Schumer told CNN Thursday in an interview in his Senate office. "His fingerprints are all over that bill. It has a lot of Rubio imprints."
Schumer, the next Senate Democratic leader, painstakingly hashed out the immigration deal with Rubio and has previously avoided lashing out at the Florida Republican publicly. But as the presidential race heats up, Schumer is unloading the new line of criticism, saying Rubio was the main architect of the provision to provide a pathway to citizenship for the nation's 11 million undocumented immigrants, something bound to give ammunition to his primary foes who call the measure "amnesty."
"He understood it, he molded it, he made it a tough path to citizenship," Schumer said. "But we all agreed to it, and it would have to be a tough path to citizenship. But he was all for it. "
Rubio spokesman Alex Conant said, "it's no secret" the freshman senator worked with Schumer and others on the controversial immigration bill. "That bill failed and has even less support now," Conant said. "The only way we can fix our immigration system is by first securing the borders."
In the wide-ranging interview with CNN Thursday, a lively Schumer also boldly predicted a Democratic wave in 2016, with Hillary Clinton securing as many as 350 electoral votes and sweeping his party back into the Senate majority. He warned the Obama administration not to put "boots on the ground" in Syria. He shed new light on his plans as the next Democratic leader, promising to be "direct" with Senate Majority Leader Mitch McConnell, with whom he has had a frosty relationship.
And after breaking publicly with the White House over the Iran nuclear deal, Schumer said "I worry" the accord is making the United States less safe but he would not back further sanctions on the regime at this time.
"Overall I don't think we should undo the agreement before it starts even though I opposed it," Schumer said when asked about new sanctions legislation.
As Clinton has seen her poll numbers falter amid the controversy surrounding her private email server, many in the party have grown unnerved that the Democratic frontrunner could blow the party's chance at taking back the White House.
The 64-year-old New Yorker was bullish about Clinton's prospects, saying that she would rout any of the GOP candidates who are seeking the party's nomination.
"I think she's going to win, and I'll stick my neck out," Schumer said. "I think she's going to get 300, 325 maybe 350 electoral votes against any of the Republicans."
Schumer added, "The hard right has such a grip on their party so ... she is going to win and win big, and I think we'll also take back the Senate for that reason."
But Clinton has seen many liberals rally behind the insurgent campaign of Vermont Sen. Bernie Sanders, who has recently stepped up his attacks against the former secretary of state's character for flip-flopping on policy issues. Schumer declined to say if Sanders should lay off those attacks, but he noted that the self-proclaimed Democratic socialist and Clinton have two very similar agendas.
"Look I have great respect for Bernie Sanders," Schumer said. "And let me tell you a lot of Bernie's platform isn't that far from Hillary's platform."
In the general election, Democrats have looked towards Rubio as the toughest candidate for Clinton, given his polish on the stump and his ability to attract younger voters and offer a generational contrast. So Democrats have seized on two aspects of Rubio's short record in the Senate: His decision to abandon the immigration bill and his frequent absences in the Senate, including Thursday when he skipped a Senate intelligence briefing where officials discussed the downed Russian airliner.
On immigration, Schumer said Rubio was "proud" of their comprehensive bill and "ran away from it so quickly" even though he put "so much work into it."
Yet Schumer wouldn't go as far as Senate Minority Leader Harry Reid, who has called on Rubio to resign because of his frequent absences.
"Every one of us runs for election, a lot, and we try to do as many votes as we can," Schumer said. "He should be voting. The amount of votes he's missed is very bad."
Relationship with McConnell and Ryan
Schumer has been resistant about talking about the expectation that he will replace Reid as the Democratic leader after next November's elections. But despite his sharp criticism of Republicans in the interview in CNN, Schumer said he would try to usher in a new era of bipartisanship, something that has been lacking in a chamber often stuck in a state of partisan gridlock.
The nearly 17-year Senate veteran singled out Sens. Lamar Alexander of Tennessee, Lindsey Graham of South Carolina and John McCain of Arizona as three Republicans with whom he would work closely to craft an agenda to "get America moving again."
Yet Schumer has had a contentious relationship with McConnell, the most powerful Republican, who, like Schumer, is his respective party's top political tactician.
"Well, I'll try to be direct with him; that's my way of nature," Schumer said of McConnell. "I'll be honest with him, and I'll say come and meet me partway."
Schumer was far less charitable about his expectations for new House Speaker Paul Ryan. While Schumer has worked with Ryan on immigration and tax reform, he said that Ryan would be pulled to the far-right by the most conservative elements of his caucus.
"I'm worried," Schumer said of Ryan. "What's going to prevail: The Paul Ryan who knows how to compromise or the Paul Ryan who has these very hard-right views on budget issues, tax issues and many other issues? My worry here is that the hard-right (Republicans will) whisper, 'I'm with you, keep it up,' (and they) will have too much power and too much weight."
Critical of the Iran deal
After Schumer announced his opposition to the Iran nuclear deal in August, he faced a barrage of criticism from the left flank of his party and the White House -- and he spoke sparingly about the matter to the media. But Schumer still opposes the deal and believes it could undermine the country's security interests.
"It was not an easy judgment," Schumer said. "And those who were so sure it was the right thing to do and those who were so sure it was the wrong thing to do are different than me. I had to weigh it very, very carefully."
Schumer, who represents a caucus strongly supportive of the deal and a pro-Israel constituency furiously opposed to it, said his decision boiled down to whether he believed the Iranian government will "moderate" as a result of the accord, something he said Secretary of State John Kerry "argued with me for a long time."
"Ultimately the risk was too great, and I opposed the deal," Schumer said.
Asked if he believed that the deal would make the country safer, Schumer added: "I hope that those who disagreed with me are right but I worry they're not."
But even as he broke with liberals on Iran, Schumer is firmly siding with the left against calls to send U.S. troops into Syria to help stem the rise of Islamic State militants.
"Anywhere we've done that in the Middle East -- it has not worked and the minute we leave it goes back to the same old status quo," Schumer said, praising the White House's current policy. "I am dubious of any combat troops on the ground."