Rep. Steve Scalise entered the home stretch of the three-way race for House majority whip in the lead, as his main competitor, Rep. Peter Roskam, shifted to a second-ballot strategy.

Less than 24 hours before Thursday's scheduled 2 p.m. vote, Scalise, the Republican Study Committee chairman, appeared to be locking down commitments from key sectors of the House Republican conference.

His newest supporters included Rep. Bill Shuster of Pennsylvania, chairman of the Transportation and Infrastructure Committee, and Rep. John Campbell of California, an RSC member who actually voted against Scalise when the Louisianan ran for chairman of that group.

Roskam, of Illinois, the current chief deputy whip, is working over supporters of Rep. Marlin Stutzman in an effort to swing them his way if Scalise doesn't win a majority on the first ballot. The Indianan, a conservative elected in 2010, is the dark horse candidate in the race for the No. 3-ranking GOP leadership post.

The Roskam team expressed confidence that the strategy would succeed, although Republicans monitoring the unpredictable contest were skeptical.

“There's still a good number of undecideds, so first ballot is still possible,” said Rep. Richard Hudson of North Carolina, one of Roskam's whip captains. “But we're also working a parallel strategy of peeling off votes for the second ballot.”

It's happened before. Nearly eight years ago, following a crushing midterm defeat for the Republicans, Speaker John Boehner of Ohio was elected House minority leader by his peers on a second ballot, after finishing second on the first ballot in a three-way race. Boehner's win over Rep. Roy Blunt of Missouri, who is now a senator, was considered an upset. Members vote by secret ballot, making whip counts potentially unreliable.

Roskam supporters concede that Roskam's position as a member of the current senior leadership team is a challenging obstacle in the wake of House Majority Leader Eric Cantor's defeat in a GOP primary in Virginia. He is stepping down on July 31, and the current majority whip, Rep. Kevin McCarthy of California, is expected to succeed him. That means the whip race is the only one in which members can inject new blood into leadership.

But Roskam partisans claim that members have reacted well to the Illinois Republican’s pitch, which they claim is ambitious and specific, and, ironically, better speaks to their desire for a change in how senior leadership runs the conference. That's why they Roskam backers they have a shot at Stutzman voters, who aren’t necessarily supporting the Indianan because he is perceived as the most conservative candidate in the race, they contend.

Sources close to Scalise dismiss Roskam’s strategy, saying flatly that it’s not viable.

These sources said that Scalise has garnered the support of a broad cross-section of the conference that includes conservatives, pragmatists, women and influential committee chairman, including Rep. Darrell Issa of California, who heads Oversight and Government Reform, House Republican Conference Chairwoman Cathy McMorris Rodgers of Washington, and Rep. Ted Yoho of Florida, who is backing Rep. Raul Labrador of Idaho over McCarthy for majority leader.

Additionally, the Scalise sources claim, the Louisianan has received commitments from a majority of the deputy whips that work under McCarthy and Roskam. This nugget is offered not so subtly to indict Roskam’s contention that he is gaining on Scalise and has the ability to beat him. Rep. Tom Cole, who is whipping for Scalise, said the choice is tough, but suggested that the Louisianan is a better fit for the job.

“He’s done a great job at the RSC,” the Oklahoma Republican said. “He has the ability to reach into the parts of our conference that sometime are a little unsettled and restive and bring them on board. He has excellent political skills.”

Stutzman, during a brief interview with the Washington Examiner on Wednesday afternoon, also said he was relying on a second ballot strategy to pull off a come from behind victory. The sophomore lawmaker pegged his support at a “solid” 50 members, and said there were probably 20 to 25 truly undecided members left out there; that number was in line with what the other two candidates’ camps were estimating.

According to House GOP rules, leadership candidates must win a majority of the conference to be elected. After the first round, if the winning candidate has less than 50 percent plus one, a second round of voting will be held immediately. The third-place candidate is eliminated from contention at that point.

“I need to get to a second ballot to win,” Stutzman said. “Then I think all bets are off.”

Washington Examiner Chief Congressional Correspondent Susan Ferrechio contributed to this report.