Fannie and Freddie: Republicans will almost certainly try, at least once, to pass a Fannie Mae/Freddie Mac amendment. The goal, at the very least, would be to scale back the government's ability to finance loans to low-income borrowers, and, at the most, to wind down the troubled firms altogether. Any such amendment will be a tough sell in the Senate, but if one slips through, it could complicate House-Senate negotiations down the line, if House Democrats don't approve (and they almost certainly wouldn't).
Consumer Protection: Likewise, the GOP will try to weaken the authority of, or even eliminate entirely, the Democrats' plan to create a new federal agency to protect consumers from predatory financial practices. This also will be a tough climb for the Republicans. But the consumer financial protection agency has become the focus of the GOP's critique of the bill in recent days, and if the Democrats shield it from any major changes, Republicans could line up to filibuster the package all over again.
Too Big To Fail: On the Democrats' side, the goals are very different. But look out for an amendment proposed by Sens. Sherrod Brown (D-OH) and Ted Kaufman (D-DE), that would put explicit limits on the size of big financial institutions. It's a long shot, and Brown himself admits that they don't have enough votes yet to succeed. But it's a popular principle, and a tough "no" vote to cast, so anything's possible.
Audit the Fed: This may be the most important of all--an amendment sponsored by Sen. Bernie Sanders (I-VT) to compel federal auditors to open up the Federal Reserve's books, to examine the toxic assets they purchased during the financial crisis and how much they (over) paid for them.
The Obama administration opposes both of these last two Democrat-friendly amendments, particularly the latter. According to the Wall Street Journal administration officials have suggested they will try to stop it "at all costs." More on this later, but its very existence creates a sticky situation no matter what happens. If the amendment passes in the Senate, then that brings the overall bill closer to the House's, which already includes an audit-the-fed provision. That could set up a tough fight between the White House and Congress. By contrast, if it fails in the Senate, then the White House and the Senate will team up to fight the House to keep audit-the-fed out of the final package.
We'll be watching these developments closely as the week goes on. Stay tuned.