(CNN) - While the eyes of the nation were trained on Boston and West, Texas, this week, lawmakers in Washington turned their eyes to two major issues.
At the same time, they contended with a poisonous threat in the form of letters the FBI said tested positive for ricin sent to President Barack Obama, a U.S. senator, and a Mississippi judge, as well as suspicious packages that turned up in the hallways of two Senate office buildings.
The Gang of Eight senators working toward a deal on immigration reform unveiled their plan this week. It immediately hit hurdles, including criticism that the months-long process was conducted behind closed doors rather than more openly.
Still, the group's members expressed optimism the deal would rise above the deep divisions in the nation's capital.
"Powerful outside sources have helped defeat other initiatives in Washington. But on immigration, the opposite is proven true," Sen. Chuck Schumer, D-New York, said while unveiling the legislation on Thursday. "I am convinced this issue will not fall victim to the usual partisan gridlock."
The sweeping reform package would impact nearly all of the estimated 11 million undocumented residents currently in the U.S. It would offer those who arrived before 2012 a 13-year path to citizenship and would require them to pay back taxes, pay a fine and pass a background check.
It would also require the administration to improve border security, a concern of many Republicans, and improve the e-verify worker verification system.
Sen. Marco Rubio of Florida, seen as a rising star in the GOP and a member of the Gang of Eight, engaged in a media blitz, appearing on seven Sunday public affairs shows and offering a series of talk radio interviews later in the week.
He sought to bring aboard conservatives who may be concerned the group's plan amounts to amnesty.
"Both Democrats and Republicans have failed to enforce the laws, and the result is we do have millions of people that are here against our immigration laws," he said at a news conference. "We're not going to deport them. So let's secure the border, and let's bring these people out of the shadows."
While immigration made an entrance on Capitol Hill, gun control legislation made an exit.
Senate Majority Leader Harry Reid said Thursday he would not bring his bill on the issue up for a final vote in the Senate after the compromise on background checks negotiated by Sens. Joe Manchin, D-West Virginia, and Pat Toomey, R-Pennsylvania, failed.
Their proposal was greatly scaled back from what Obama and many gun control proponents initially proposed after the December mass shooting at a Newtown, Connecticut, elementary school.
But the expansion of background checks to sales made online and at gun shows was considered most likely of all gun-related restrictions to muster the necessary bipartisan support to succeed.
Obama said he supported the compromise - though he wanted it strengthened, - and after it failed, he chastised those who voted against it.
"All in all, this was a pretty shameful day for Washington," he said, surrounded by families from Newtown.
Reid could pull the bill off the shelf if he believes he has enough votes for it to pass either as-is or amended, and he said he hoped the senators would continue their negotiations.
The stalling of the Senate bill also means the House gun legislation is all but dead.
But immigration will resurface on the Hill this week and Congress also digs into Obama's budget proposal with a series of hearings.
– CNN's Gregory Wallace, Dana Bash, Ashley Killough and Kevin Liptak contributed to this report