Updated

A shockwave like this one hasn’t ripped across Indiana’s cornfields since Bob Knight hurled a chair onto the court in a game against Purdue.

The Hick from French Lick didn’t generate a buzz like this when he jumped center against Magic Johnson in the 1979 NCAA title game.

Even Mary Fendrich Hulman’s command of “Gentlemen, start your engines!” at the Indianapolis 500 seems anticlimactic compared to this.

Sen. Evan Bayh (D-IN) shocked the state Monday with his retirement announcement from the Senate.

But his stunning decision to quit after two terms could reverberate well beyond the banks of the Wabash.

Evan Bayh is a moderate Democrat who was expected to win re-election in what could prove to be a tumultuous year for his party. His retirement instantly threw the seat into “tossup” category, according to political handicapper Stuart Rothenberg. The Cook Political Report goes even further, indicating Bayh’s seat “leans Republican.” And that means that Democrats are now facing the very real prospect of potentially losing control of the Senate this fall.

However, Bayh’s retirement could spell potential disaster for House Democrats too. Perhaps even President Obama in 2012. To paraphrase Hoosier minstrel John Mellencamp, Indiana could be where walls come crumbing down on the Democrats.

Indiana is a case study of how Democrats surged nationally in the past two election cycles. In 2006, Democrats gained a majority of the state’s nine House seats as Reps. Baron Hill (D-IN), Brad Ellsworth (D-IN) and Joe Donnelly (D-IN) toppled three Republican incumbents. Their victories were a harbinger of the 2008 presidential election. Mr. Obama edged out Sen. John McCain (R-AZ) by a single percentage point in Indiana. It was the first time the state voted for a Democratic presidential nominee since 1964.

But Bayh helped set the stage for the Democrats’ success with his re-election in 2004.

President Bush won the state that year with nearly 60 percent of the vote. Democratic presidential nominee Sen. John Kerry (D-MA) polled just under 40 percent. Bayh grafted his advocacy for a strong, national defense to his fiscal and social conservatism. Those stances resonated with Indiana voters and helped burnish the path for Hill, Ellsworth and Donnelly two years later. And all are cut from the same political cloth as Bayh.

Early Monday, there was chatter that any of these three House members could jump into the fray to be the state’s Democratic nominee for Senate. So far, only Ellsworth is considering the bait. In a statement, Ellsworth said that he will take “a few days to talk to my wife and to folks in Indiana about where I can best serve our state.” Donnelly says he’s running for re-election to the House. Hill’s spokeswoman, Katie Moreau, did not return messages trying to gauge her boss’s interest in succeeding Bayh.

But regardless, a potential Republican surge could create challenging circumstances for all three as Indiana swings in the balance.

First, voters will scrutinize their voting records. All three voted for the health care reform bill in December. And it will bear watching to see if any or all of them support a retrenched health bill, if it ever sees the light of day in the House. Among the three, only Baron Hill voted for the controversial climate legislation, described by some as “cap and trade.”

Hill is facing off for the fifth consecutive time with former Rep. Mike Sodrel (R-IN). Hill beat Sodrel twice before the Republican unseated him in 2004. Hill rallied to take the last two contests, skunking Sodrel by 20 points in 2008. But Hill garnered just 51 percent of the vote or less in three of his five successful House campaigns. And in late January, the Cook Political Report shifted Hill’s seat into the tossup camp.

Cook places both the seats of Donnelly and Ellsworth in the “lean Democratic” category. In fact, Donnelly captured a whopping 67 percent of the vote in his northern Indiana district. Ellsworth secured nearly 65 percent of the vote in his. Both of those figures are astonishing considering that those districts swung from Republican to Democratic in 2006. Note that Rep. Andre Carson (D-IN), who represents Indianapolis, the most urban district in the state, secured only 65 percent of the vote himself with President Obama heading the ticket. One noted GOP insider conceded two weeks ago that it would be tough to beat Ellsworth, regardless of this year’s political dynamic.

Indiana nearly doubled its 2004 voter turnout in the 2008 presidential contest. And without the president atop the ballot this fall, it’s doubtful Ellsworth and Donnelly will score winning percentages anything close to what they won with last time. Plus, it’s likely political soothsayers will immediately consider either the districts of Hill or Ellsworth as tossups should either of them run to succeed Bayh.

If a GOP wave starts washing through rural districts in New York, Pennsylvania, West Virginia and Ohio, it will crash through Indiana. Success in Hoosier country is one of the reasons Democrats seized control of the House in 2006. Bayh’s 2004 re-election helped Democrats win the Senate in 2006. And the applicable corollary here is that Bayh’s retirement makes his home state a critical proving ground in this election.

In the basketball classic “Hoosiers,” Gene Hackman plays down-and-out high school basketball coach Norman Dale. Dale is given a last shot at coaching in a rural Indiana community that eats, sleeps and breathes basketball. In the film, Hackman doles out some sideline advice to his squad during a timeout.

“Stick with your man,” he admonishes. “Think of him as chewing gum. By the end of the game, I want you to know what flavor he is.”

As in 2006 and 2008, Indiana could again prove to be a political bellwether for the country. The winds are favoring the Republicans. And you can expect voters to be much like Hackman’s team, shadowing their lawmakers up and down the court, listening to what they say and watching how they vote.

After all, they want to know what flavor they are come November.

-         Chad Pergram covers Congress for FOX News. He’s won an Edward R. Murrow Award and the Joan Barone Award for his reporting on Capitol Hill.

-         The Speaker’s Lobby refers to a long, ornate hallway that runs behind the dais in the House chamber. Lawmakers, aides and journalists often confer there during votes.