Should the Democrats gain control of one or even both chambers of Congress in next month’s elections, their leaders will have a hard time imposing a liberal agenda on America.

If the Republican nightmare becomes reality and Nancy Pelosi ascends to the role of House Speaker in January, she will preside over a razor-thin majority comprised of some Democrats from conservative districts who won’t vote in lock-step with her. Even if she is able to create rock solid discipline within her party, any legislation passed by the House must move to the Senate, where Republicans can gum up the works even if they find themselves with minority status. To become law, any legislation would still have to withstand a presidential veto, and unless President Bush is convicted of having committed, “treason, bribery, or other high crimes and misdemeanors,” he will reside in the White House for another two years.

When they wrote the U.S. Constitution, our country’s founders intentionally designed a system that makes it difficult for broad, sweeping changes to be made based on short-term passions. For more than two centuries, this has helped preserve liberty and foster a remarkable stability that has enabled America to evolve into the most prosperous nation in the world. But liberals know that the Constitution is the biggest obstacle they face to imposing their progressive vision on our country, which is why they have fought for decades to undermine the document. Now, a University of Texas law professor and self-described “strong Democrat” is arguing that we should scrap it altogether.

Sanford Levinson, author of the new book, Our Undemocratic Constitution: Where the Constitution Goes Wrong (and How We the People Can Correct It), wrote in the Los Angeles Times this week that “the Constitution is so far from perfect that it threatens our ability to resolve the daunting problems facing our society.” Because it’s too difficult to amend our founding document under current rules, and even then we can only make small changes, his solution is for a new Constitutional Convention during which the whole document would be fair game.

One can just imagine the circus such an event would create in today’s political environment. Harry Reid on C-Span accusing Republicans of wanting to write a Constitution “of the rich, by the rich, and for the rich,” and Dick Cheney firing back that Democrats want a constitution that will embolden Al Qaeda. CNN running a “Constitutional Crisis” graphic (cue ominous music), while FoxNews holds lively debates: “‘Necessary and Proper’ clause: Keep it or Dump It? We report. You decide.”

Moving beyond the impracticality of such an endeavor, it’s worth examining some of the specific problems Levinson has with the Constitution. One of his major complaints is the existence of the U.S. Senate, which gives disproportionate influence to smaller states to the detriment of more populous states, resulting in the flow of tax dollars to projects such as Alaska’s “bridge to nowhere.” However, the root cause of such a project is not the existence of the Senate, but the prevalence of the ideology of big government that originated with liberals and has recently been adopted by Republicans.

Were the Senate abolished in favor of a system of purely proportional representation, the only thing that would change is that California and New York would have free rein to siphon money away from smaller states to pay for their own pet projects (not to mention impose their views on everything else on smaller states). Under the current system, California and New York can still throw their weight around the House of Representatives, but through the Senate, the smaller states harness the ability to block policies that they find particularly objectionable.

Levinson also faults our system for not having “mechanisms by which leaders who lose the public’s confidence can be removed” (i.e. Bush is still president despite low approval ratings), and he laments that the power to veto legislation allows the president to “become an independent third house of an already cumbersome legislative process.” This “cumbersome process” he says, helps explain “the difficulty — often, the impossibility — of passing innovative legislation and having it signed into law.”

This is exactly right, and how things should be. As James Q. Wilson wrote in TAS‘s September issue:

America was slow to adopt welfare programs, social security, unemployment insurance, and government-supported health care, while Europe adopted these policies rapidly. We have kept our tax rate lower than it is in most of Europe. The central difference is not that Europeans are either smarter or dumber than we, but that a parliamentary system permits temporary popular majorities to make bold changes rather quickly, whereas a presidential system with a powerful, independent, and internally divided Congress requires that big changes undergo lengthy debates and substantive accommodations.

Eventually, America did adopt many welfare programs (mainly during two periods in our history when Democrats held huge majorities that enabled the American government, in Wilson’s words, to “act like a parliamentary system”), but America has not degenerated into a full-fledged European welfare state largely because of the way our Constitution was written.

This may be bad news for progressives, but even those of them who are eager to tear up the U.S. Constitution and start all over should consider that a parliamentary system cuts both ways. Liberals may have been frustrated by their inability to achieve universal healthcare during the Clinton years, but if America were a parliamentary system, they would have woken up to the reality of a Prime Minister Gingrich the morning after the 1994 elections. Had it not been for the “cumbersome legislative process,” Democrats would have found it much more difficult — if not impossible — to stop Social Security privatization last year.

Obviously, it still makes a difference what party is in power. Should Democrats emerge victorious next month, they will likely investigate President Bush aggressively and block attempts to make his tax cuts permanent. But Republicans will still have an arsenal of tools at their disposal to stymie the Democrats. And for that, we have the founders to thank.