Senate Majority Leader Harry Reid's decision to schedule a vote to bring gun legislation to the floor Thursday coupled with the news this morning that a bipartisan agreement had been reached on expanded background checks is being touted by advocates of gun control as a major step in the right direction.

Advocates of stricter gun control measures.

Maybe they're right. But, maybe they aren't.

Let's assume that enough Republicans refuse to sign on to the filibuster effort being led by Sens. Ted Cruz (R-Texas) and Rand Paul (R-Ky.). (At the moment, at least eight Republican Senators are on the record saying they will vote for cloture.) That means that if Reid can keep all 55 Democratic-caucusing Senators in line, he should have more than the 60 votes he would need to end unlimited debate -- bringing the bill to the floor and allowing amendments to it to be offered before a final vote on passage.

While such a turn of events is being cast as a major win for Democrats and the White House against the forces of Republican opposition, there's a strong case to be made that an open amendment process to the gun legislation might well doom it.

"Republicans are eager to get into an open amendment process so that they can turn a responsible gun control bill into a round of NRA-backed amendments that only need 51 votes to approve," warned one senior Democratic operative granted anonymity to speak candidly about strategy matters. "This could be a nightmare for Democrats that care about these issues."

The thinking goes like this. There are very few "swing" Republican votes on guns. (Of the 14 Republican Senators/seats up in 2014, only Maine's Susan Collins represents a state President Obama carried in 2012.) On the other hand, there are a number of "swing" Democratic votes on guns -- with 5 Democratic incumbents running for re-election in states Mitt Romney won last November.

And, there are plenty of examples in the not-too-distant past of how much support gun rights legislation has had on the Senate floor.

In the fall of 2009, Senate Republicans offered an amendment to an appropriations bill funding transportation projects that would have allowed people to bring guns on to Amtrak trains. At the time, Democrats controlled 59 seats in the Senate while Republicans held 40. (Ted Kennedy had passed away but no replacement had yet been named.) The amendment got 68 "ayes", meaning that 28 Democrats voted for it.

A few months earlier, in May 2009, Oklahoma Republican Sen. Tom Coburn introduced an amendment that would have allowed guns to be carried in national parks. Democrats had 56 members voting (four seats were either vacant or the incumbent was too ill to vote) to 40 for Republicans.  The bill got 67 "ayes" with 27 Democrats supporting it. (Twenty nine Democrats opposed it.)

Given that math, it's easier to imagine amendments favored by gun rights advocates generating the 51 votes needed to be added to the main legislation than amendments on things like renewing the assault weapons ban or limiting (or outright banning) high capacity magazines.

Of course, Democrats could try to force 60-vote thresholds on pro-gun-rights amendments but that could also threaten to unwind the entire legislation in a procedural quagmire that leaves the final bill failing to muster the 60 votes needed for final passage.

So, yes, the bipartisan deal on background checks, which is expected to be the first amendment offered to the overall gun bill, is a victory for those who want stricter gun laws. But, the amendment process has the potential to turn into something far different than gun control advocates imagine -- and something that would almost certainly doom the legislation.