WALL STREET REFORM: ONE STEP FORWARD, ONE STEP BACK?…. As of late yesterday afternoon, the pieces appeared to be in place to finally complete work on Wall Street reform. The majority had 57 Democratic votes — the entire caucus, sans Russ Feingold (D-Wis.) — and needed three Republicans. Maine’s Susan Collins endorsed the bill last week; Massachusetts’ Scott Brown agreed yesterday morning; and Maine’s Olympia Snowe announced her support late in the day. It seemed 60 votes were in place.

Indeed, soon after Snowe issued her statement, Senate Majority Leader Harry Reid (D-Nev.) announced, “We will finish our work on this bill this week to ensure that these critical protections and accountability for Wall Street are in place as soon as possible.” It seemed a Thursday floor vote was likely.

But as we’ve learned, nothing is ever easy in the Senate.

Senate Majority Leader Harry Reid (D-Nev.) vowed Monday to move forward with a financial regulatory overhaul this week, despite last-minute waffling by Sen. Ben Nelson (D-Neb.) that could throw that schedule into doubt…. Reid needs the support of Nelson, who is suddenly showing signs of wavering.

Specifically, Nelson said late yesterday, “You don’t know who’s going to be head of the consumer protection bureau. You can’t just send a rogue agency out on its own.”

The comments were a reminder that of why Nelson is so often a confounding disappointment. The provisions related to the consumer protection agency have been debated for months. He waited until the week of the vote, after 60 votes were in place, to start making threats? After he already voted for the same provisions a month ago?

It’s very likely this is yet another attempt for the conservative Nebraskan to gain leverage over his colleagues. Here’s an idea: maybe Ben Nelson should hold the bill hostage until he works out a secret deal behind closed doors that gives him unique influence over the process. That worked out for him so well the last time he tried such a stunt.

Roll Call reported this morning that Democratic leadership aides are “confident they can persuade Nelson to vote for the measure and deliver on Reid’s vow to finish the bill this week.” If Nelson betrays the party again, the leadership will either a) find another Republican supporter, which seems highly unlikely; or b) wait until next week, when the late Sen. Robert Byrd’s (D-W.Va.) temporary replacement is expected to be in place.

Update: As of late this morning, it looks like Nelson will vote for Wall Street reform. Barring any 11th-hour surprises, the legislation should pass this week, and Reid will start the clock today.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.