This week's vote on the Manchin-Toomey compromise on background checks — expected either Tuesday or Wednesday — will determine if substantive gun control legislation has a chance of becoming law.

Although the bill was mocked by Saturday Night Live over the weekend, it's still the last best hope gun control advocates have to pass new gun restrictions.

But the hurdles are enormous.

The Manchin-Toomey amendment will need at least 60 votes to pass, and Senate Majority Leader Harry Reid will have to fight off numerous "poison pill" amendments since he promised an open process for modifying the bill.

But even if the Manchin-Toomey proposal clears the 60-vote hurdle and the amendments process, the legislation faces an even bigger obstacle down the road: the Republican-controlled House of Representatives.

As First Read notes, House Speaker John Boehner has been willing to violate the so-called "Hastert rule" and bring legislation to the floor that isn't supported by a "majority of the majority" — as long as it has 70 or more votes in the Senate. Right now, however, the Manchin-Toomey measure is nowhere close to getting that number.

The latest whip count shows 53 senators support the bill while 36 oppose it, and 11 are unknown. Even if all the undeclared senators vote in favor, it's nowhere near the 70-vote threshold that might pressure Boehner to give the bill a vote in the House.