Go over and read how Ed Morrissey's innocent question to Sen. John McCain in a media conference call led to a significant new hurdle for the Senate immigration bill. This is the end result:

House conservatives are ready to stop the Senate immigration bill in its tracks with a potent procedural weapon should the contentious measure win passage in the upper chamber.

The trump card conservatives may hold is a constitutional rule that revenue-related bills must originate in the House. The Senate immigration measure requires that illegal immigrants pay back taxes before becoming citizens, opening the door to a House protest, dubbed a 'blue slip' for the color of its paper.

This has happened before. In fact, it happened less than a year ago, with the same piece of legislation. The Senate included a provision in its version of the immigration bill to require the repayment of back taxes. This led the House to 'Blue Slip' the measure, forcing the Senate leadership to find a procedural work-around.

The Senate is not entirely without moves of its own that it can make. The House has passed a few tax bills this year that the Senate might 'amend' by adding the immigration bill. This would create a significantly broader piece of legislation--but it would technically satisfy the Congressional stipulation that revenue bills originate in the House of Representatives.

Alternately, leaders from the House and Senate might strike a bargain in advance, and have the Senate strip the tax provisions before sending the measure to the House--with the understanding that the House would add them back in later.

Lastly, Don Wolfensberger--a former Staff Director for the House Rules Committee and a procedural whiz--wrote last year ($) that the House can vote to ignore the violation--more or less:

If the Senate, either intentionally or inadvertently, originates a revenue-raising bill, any Member of the House has the option of calling up a 'blue-slip resolution' (named after the color of paper it is printed on after passage) to send the measure back to the Senate. The resolution gets immediate consideration as a matter of constitutional privilege, is debatable for an hour and is not subject to amendment (though it may be tabled or referred to committee).

If the political will exists, there are several ways for the Senate to eliminate this problem and expedite passage of the measure. However, for legislation that's none too popular already, this is a problem its proponents ought to have tried harder to avoid.