Senate Republicans, along with GOP lawmakers in the House, know that Sen. Ted Cruz and his colleagues don't have the votes to pass a continuing resolution to defund Obamacare. They don't even have the votes -- 41 in the Senate -- to successfully filibuster a resolution that does fund Obamacare. But some had hoped that Cruz & Co. could at least stage an old-fashioned talking filibuster -- like Sen. Rand Paul's March filibuster against U.S. drone policy -- that would at least be a high-profile symbol of Republican opposition to the president's national health care law.

Now, it turns out they can't even do that. "We won't have an opportunity to filibuster," says a Senate Republican aide. "It's going to be a simple majority vote."

As the aide explained it, when the House passes a continuing resolution that defunds Obamacare and sends it to the Senate, several things will happen. There will be cloture votes on a motion to proceed and a motion to actually take up the defunding resolution. The bill will almost certainly go forward; Republicans, whatever their position on the defunding question, certainly won't stop the House bill before it can be considered.

Then, when the defunding continuing resolution is being considered, Senate Majority Leader Harry Reid will propose a motion to strike the defunding provision from the continuing resolution. Senate rules allow that to be decided on a simple majority vote. Democrats will vote to strike the defunding portion and set up a final up-or-down vote on the continuing resolution, which at that point will be just a measure to fund the government, including Obamacare. There will be a simple majority vote. The measure will pass.

But couldn't Cruz and his allies stand up and stage a talking filibuster, at least to put the process on hold? In fact, Senate rules, which Reid will enforce, will limit the debate on the measure to 30 hours, divided evenly between the parties. That gives Republicans 15 hours, to be divided between 46 GOP senators. That's not a lot of time. It's possible the Republican caucus could decide to allow Cruz to filibuster for an extended period of time. But it's unlikely, given the other senators who will likely want to speak out on the issue. In March, the Rand Paul filibuster went on for nearly 13 hours; don't look for something like that to happen this time.

So Republicans don't have the votes to actually filibuster a continuing resolution, and they don't have the rules on their side to stage a talking filibuster. Supporters of defunding are bound to be disappointed. But the Senate aide says no one should be surprised. "This is not a gimmick or a scheme," says the aide. "It is Rule 22 of the U.S. Senate. Everybody knew this. This is an existing rule. It is taught in Senate class when you do your orientation. It is not a surprise. Nobody sprung it on him [Sen. Cruz]."

The bottom line is, as the prospect of an actual legislative battle over defunding nears, it's becoming more and more apparent that Sen. Cruz and his allies have very few options. In the end, it's not likely to be much of a battle at all.