The main event at Thursday’s House Republican leadership races is a three-way battle for majority whip. The whip post isn't the most high-profile job, but history tells us these are often ripple-effect races, moments in time when second-tier lawmakers battle for second-tier posts, with the victors eventually shaping the next few decades in terms of life under the Capitol dome.

No one should expect Rep. Steve Scalise (R-La.) to become the next Trent Lott or Rep. Peter Roskam (R-Ill.) the next Tom DeLay, but the opportunity is there. Over the last 50 years, each of the four congressional caucuses has held an epic race for whip that reverberated for years to come. [For a recap of the 10 greatest leadership races ever, as Roll Call declared in 2005, see this story by our friend Ben Pershing.]

Here’s a recap of the four most important whip races, in descending order:

Nancy Pelosi vs. Steny Hoyer for House Democratic whip (2001)

This whip race may hold the record for longest leadership battle. The ballots were cast in the fall of 2001, but these two rivals began their fight in early 1999 angling for a different post: majority whip. Democrats needed just six seats to pick up the majority in November 2000, in which case Dick Gephardt would become speaker, David Bonior the leader, and an opening would emerge for whip.

U.S. House Minority Leader Nancy Pelosi (D-CA) speaks to the press about the potential for a U.S. government shutdown, alongside House Minority Whip Steny Hoyer (D-MD), U.S. Rep Peter Welch (D-VT) and Rep. James Clyburn (D-SC) (L-R), at the U.S. Capitol in Washington, September 25, 2013. REUTERS/Jason Reed

They fought for two years, furiously raising money for each other’s allies and for neutral lawmakers. All for naught: Democrats fell short; the leadership ladder stayed the same. Yet when Bonior retired from whip to run for governor, the battle was joined again. The campaign set the future of the House Democratic caucus, firmly positioning it as more coastal and aligned with the environment and new technologies. Hoyer’s allies consisted of old bulls such as John Dingell (Mich.) and Martin Frost (Tex.), but Pelosi won by 23 votes. The rest is history: she succeeded Gephardt as minority leader, became the first  woman House speaker and proved to be the political backbone behind pushing President Obama and wavering Democrats to pass the health-care law in 2010.

Hoyer, who had previously lost the whip race to Bonior in 1991, finally won the post in 2003 and has served as Pelosi’s No. 2 for the last 11 and a half years.

Trent Lott vs. Alan Simpson for Senate GOP whip (1994)

Just having finished his first term in the Senate, Trent Lott (Miss.) took advantage of the huge new influx of younger Republicans who won in the GOP wave of 1994 and ran for majority whip. In doing so, Lott -- 53 at the time -- ran against Alan Simpson, then 63, who had spent 10 years as the loyal whip to Bob Dole (Kan.) and was deep into his third term.

Lott’s challenge was part generational, part ideological style, a different breed of Republican than the more congenial Dole. "When Trent wants something, he goes after it with great gusto," Simpson later told The Post’s Helen Dewar. Lott worked the newcomers hard -- a class that included staunch conservatives such as Rick Santorum (Pa.), Jim Inhofe (Okla.) and John Ashcroft (Mo.) -- and won by a single vote. Lott won a huge victory a year later to succeed Dole after he resigned to claim the GOP presidential nomination, defeating home-state rival Thad Cochran.

Lott, who eventually resigned as GOP leader after intemperate remarks at Strom Thurmond’s 100th birthday party, gained a reputation as one of the Senate's foremost deal-brokers. Welfare reform, a minimum wage hike, the 1997 budget deal and a massive rewrite of telecommunications laws passed under his watch. And now, almost 18 years to the day that he defeated Cochran for leader, he is appearing in ads trying to save Cochran from defeat in next week’s Mississippi primary runoff.

Ted Kennedy vs. Robert Byrd for Senate Democratic whip (1971)

No whip race can claim two such historic figures battling it out as this one from January 1971. It’s easy to remember their last years working together on everything from opposing the Iraq war to passing health care. "Banish the germs and hurry back," Kennedy wrote in June 2009 to Byrd, two months before Kennedy died. "West Virginia needs you, the Senate needs you, the nation needs you, and so do I.”

Sen. Edward M. Kennedy (D-Mass.), stands beside his sister, Jean Smith, at a topping out ceremony at the John F. Kennedy Center for the Performing Arts in Washington, Sept. 30, 1968. (AP Photo/Bob Schutz)

But the two legends spent decades as rivals. Elected in 1958, Byrd threw himself in with the Southern Senate Democrats, becoming a fervent supporter of then-Majority Leader Lyndon Johnson’s presidential bid. When the race came to West Virginia, Johnson didn’t even contest the state, but Byrd threw his support behind Hubert Humphrey, hoping to dent John F. Kennedy’s momentum. Instead, Kennedy won big there and eventually claimed the Oval Office. Two years later, Edward M. Kennedy won his brother’s Senate seat and aligned himself with the burgeoning liberal wing. After the 1968 elections, the young Kennedy ousted Russell Long (La.) as Democratic whip – a defeat that stunned the Southern flank.

The undercurrent was that Edward Kennedy would use the post to launch a presidential bid, and the Southerners quickly grew at ease with another Kennedy running. By the summer of 1969, Kennedy had his infamous car crash on Chappaquiddick Island, adjacent to Martha's Vineyard, killing his female passenger, and he was badly injured, taking time away from the Senate.

Byrd pounced when the next elections were held, challenging Kennedy for whip. Richard Russell (Ga.), on the verge of death at Walter Reed Army Medical Hospital, was allowed to cast a vote by proxy – a vote that, Byrd told reporters, secured him the majority and brought along a couple others. He won, 31-24.

Kennedy exited the meeting and told reporters he would go back to his committees and dedicate himself to “the cause of my life,” passing health-care legislation, a phrase he would repeat for nearly four decades. Byrd went on to become majority leader and eventually Appropriations Committee chairman.

With both their ambitions tamed, Byrd and Kennedy eventually became elder statesmen and friends, both falling gravely ill in 2008 and 2009. By December 2009, Democrats needed all 60 votes to break multiple GOP filibuster attempts. “This is for Teddy,” a frail Robert C. Byrd would whisper to his aides as they wheeled him into the chamber.

Newt Gingrich vs. Ed Madigan for House GOP whip (1989)

No leadership race has likely ever had this much ripple effect. It set the entire plate tectonics of Republican politics for the next 25 years. Don’t believe us? Read on.

The minority whip job opened after the 1988 elections because Minority Whip Lott grew tired of waiting for Republicans to win the House majority and won a Senate seat. Republicans rallied around a smart, lower-key successor: Rep. Richard Cheney (Wyo.). But the new George H.W. Bush administration ran into major problems with its selection of John Tower, the former Texas senator, to become defense secretary, amid allegations of poor personal behavior, and the Senate Democrats rejected his nomination. Desperate to find someone who could win confirmation, the Bush White House plucked Cheney from his House minority whip post and nominated him -- setting Cheney on a path for two Iraq wars, eight years as vice president and countless controversies about the second Bush administration’s foreign policy.

NEW ORLEANS, LA - MAY 30: Former Speaker of the House Newt Gingrich speaks at day two of the 2014 Republican Leadership Conference on May 30, 2014 in New Orleans, Louisiana. (Photo by Justin Sullivan/Getty Images)

With Cheney running the Pentagon, House Republicans faced a choice between a solid Midwesterner in Madigan (Ill.) and the more combative Gingrich (Ga.), who had spent the previous few years waging an ethics war against Democratic leaders. Madigan’s campaign was run by two back-bench Republicans named Tom DeLay (Tex.) and Dennis Hastert (Ill.).

Stuck in the minority since 1954, 87 Republicans threw their support to Gingrich, two more than Madigan, a stunning rebuke to Minority Leader Bob Michel (Ill.). Even some moderate Republicans such as then-Reps. Olympia Snowe (Maine) and Larry Coughlin (Pa.) supported the confrontational style Gingrich promised to deliver. “We've elected probably the primary proponent of the possibility of Republican majority,” Rep. Vin Weber (Minn.) told Robin Toner of the New York Times.

Weber was right, but it took until 1994 for Republicans to claim the majority. DeLay never quite got over the Madigan defeat and ran his own insurgent campaign against Gingrich. He narrowly beat Gingrich’s closest ally, Bob Walker (Pa.), to become majority whip. That feud played out in coup attempts against Gingrich and ultimately led to DeLay hand picking Gingrich’s successor as speaker: Hastert, who ended up serving eight years with the gavel, longer than any Republican ever.

What would have happened if John Tower had won Senate confirmation and left Cheney in the House? Or if Lott had never wanted to be a senator and stayed in the House? Or if Madigan could have locked down more votes from moderates and his own state?

''The truth is, I represent a general mood and a general direction,” Gingrich said presciently at the time.