The reason: The large and fast-growing Hispanic electorate, who gave Bush nearly 40 percent of their vote, would be angered and activated as never before by a House bill that would turn illegal Hispanic workers into felons. Most of that vote would go to the Democrats this time, and that could topple some of the GOP's most vulnerable candidates in the fall.
What we have shaping up here is a damned-if-you-do, damned-if-you-don't political conundrum from which there are few sure-fire options.
If conservative Republicans were to cave in to most of the elements in the Senate bill, it could risk alienating a significant portion of their already badly divided base.
If the GOP tried to go with an enforcement-only bill along the lines of what the House has passed, it would turn Hispanic voters against them for years to come.
If Congress does nothing this year about an issue that has been driven to the top of the agenda, an already angry electorate would have further reason to throw out a lot of marginal incumbents, which could threaten GOP control of Congress.
Still, this doesn't mean that a skillfully written House-Senate compromise couldn't thread the needle and appeal to enough lawmakers with a bill that is tough on enforcement now and includes long-term reforms in the years to come.
This is where some skillful political leadership is needed, something that is sorely lacking on both sides of this debate.
My guess is that the public is ready to support a more comprehensive reform that has some limited legal, card-carrying temp worker system and a tough-love, back-of-the-line citizenship road for illegals who have lived and worked here for years.
Americans want Congress to fix the problem of illegal immigration, and they will have little patience with lawmakers who say they tried but could not reach an agreement on a sensible, long-term solution.
I agree with South Carolina Sen. Lindsey Graham, who says, "To do nothing is a political loser."