The most extraordinary thing about Al Franken's first term in the U.S. Senate may be what an ordinary member of Congress he has become.

The sharp-tongued satirist, who made his political name mainly through name-calling — dubbing Republicans and conservatives "lying liars," and "big fat idiots" and other more profane and childish things — has improved his manners and his haircut, immersed himself in the intricacies of health care and financial reform, net neutrality and job training, and become as earnest, dignified and dull as any other Washington peacock.

And there's one other way Franken has become a typical climber on Capitol Hill: He almost always votes in lockstep with the majority of his party, demonstrating all the independence of mind of a well-trained rooster pecking the proper button to obtain a kernel of corn.

If you pay any attention to politics, you've probably already heard that Franken "has voted with President Obama 97 percent of the time." If not, you soon will. Now that the general election campaign is underway — with Republican primary voters last week confirming investment banker Mike McFadden as their challenger to Franken in November — it's plain that the Democratic incumbent's "rubber stamp" ways will be a central line of GOP attack.

Unlike all too many political attacks, this charge is substantially accurate. But exactly like too many, it is not the whole story. In today's hyper-polarized, gridlocked Congress, nearly every member, Republican or Democrat, is a rubber stamp for his or her party. Franken stands out in this only the way an especially adorable puppy stands out — or an especially stinky skunk.

According to Congressional Quarterly majority Democrats in the Senate set a record in 2013 for voting as a block. On average they supported the party position 94 percent of the time. In the House, majority Republicans likewise reached a record average last year, at 92 percent.

It's true that even among these herd animals, Franken's voting behavior has been notably predictable. A Washington Post congressional database indicates that so far in the 113th Congress (2013-14), Franken is one of 11 senators to vote along party lines 99 percent of the time — a few percentage points higher than his scores in the previous four years.

But differences in this tendency are slight, even comparing Franken with other Minnesotans. Sen. Amy Klobuchar, often credited with a bipartisan temperament, scores 98 percent party loyalty in the Post's current tally, and has been above 90 percent throughout her tenure.

Meanwhile, in the House of Representatives, seven of Minnesota's eight representatives — Republicans and Democrats both — have voted with their party at least 90 percent of the time in the current Congress, as they nearly always have in recent years.

The exception is 12-term, "Blue Dog" Democrat Collin Peterson from Minnesota's rural Seventh District. The Post database reveals him as the second-least-reliable party-line vote in the current House, at just 68 percent. Peterson's voting record hasn't always been quite that independent, but he is undoubtedly a surviving maverick from an era when his kind was much more common.

Many analysts have shown that today's rigid partisan battle line in Congress is something new, often adding that this might help explain the institution's plunging popularity. The change is vivid in the history of Minnesota's delegation.

In the 103rd Congress, 20 years ago, only four members of Minnesota's 10-member delegation were 90-percent-plus rubber stamps for their parties (four others scored under 80 percent).

Today, nine of our 10 vote pretty much the way they're told.

Party discipline isn't all bad. It helps citizens understand what they're voting for when they darken an oval for a Democrat or a Republican. Yet as I've fretted here before, the extreme ideological purity that has transformed our once diverse political parties may be proving ill-suited to America's system of government, with its structurally divided powers and many checks and balances.

It's a system where compromise and dealmaking across party lines — party defections, in other words — are almost indispensable to enacting legislation and solving problems. Strict party discipline often means paralysis.

Anyhow, voters must face the choices they have. Some candidates may possess blinding policy insights, irresistible eloquence, or the blend of charm and shrewdness that can break through gridlock. But mostly members of Congress cast votes. And voters' choices today are usually between Democratic rubber stamps and Republican rubber stamps.

As it happens, GOP voters last week had the option of nominating state Rep. Jim Abeler, a politician with a proven record of occasionally defying party orthodoxy. Instead they overwhelmingly chose McFadden, a first-time candidate unburdened with a public record.

McFadden seems eager to insist that he has a mind of his own. It's rather less clear whether he's made up that mind. In an appearance last week, according to a news report, McFadden chastised Franken for being Obama's lackey and also Republicans who "can't work with the president" — implying that a Sen. McFadden would cooperate but not capitulate. Less encouragingly, he then suggested that he might support a road-building gas tax increase, offset by tax cuts elsewhere — only to quickly retreat from that hint of heresy against no-new-taxes dogma and "reiterate" that he in fact opposed any gas tax hike.

Any questions? Well, the campaign is only beginning. Franken's lopsided voting record obviously will be debated, as it should be. But if McFadden intends not just to run with a different partisan herd but to promise a more independent approach to the work of the Senate, now would be the time to clarify what that might mean.

D.J. Tice is at Doug.Tice@startribune.com.