The one-time foes are expected to hit the trail together this Saturday, with Lumaj helping McMahon christen her new campaign office in Norwalk.
McMahon opened up a 29-point lead on former Congressman Christopher Shays last week in the latest Quinnipiac poll of registered Republicans, who endorsed the wrestling mogul by a 2-to-1 margin at the state party convention in May.
An immigration and criminal lawyer, Lumaj, 44, gained the distinction as the first Senate candidate born in Albania.
"I think, at this point, it's time for the party to unite," Lumaj said. "I wouldn't hesitate to endorse her at all."
The winner of the Republican primary, which is scheduled for Aug. 14, could face U.S. Rep. Christopher Murphy, D-5, in the general election.
Murphy must first get past former Secretary of the State Susan Bysiewicz in the Democratic primary.
Lumaj received just 22 of 1,208 delegates at the state GOP convention, well below the 15 percent threshold required to automatically qualify for the primary.
"I am so grateful to have the support of Peter Lumaj," McMahon said in a statement. "He ran an honorable campaign and made history as the first Albanian-born American to run for U.S. Senate. We agree it is time for the party to unify around our shared goal of defeating Congressman Murphy in November. I look forward to working with him to promote my plan for creating jobs and restoring the economy."
He could have petitioned his way onto the ballot by collecting signatures from 8,319 of the 415,917 registered Republicans statewide.
The deadline was June 12, however.
"I don't see that as a good thing to do at this point," Lumaj said of primarying.
Before the state party convention, Lumaj questioned how much McMahon had to do with the boom of her family's professional wrestling empire, WWE, the Stamford-based company previously known as World Wrestling Entertainment.
He even prepared to launch a television ad attacking the GOP frontrunner and two-time Senate contender.
"I think that would have been damaging to the main campaign if I started attacking her," Lumaj said. "A campaign is a campaign. For the sake of the party and for the sake of unity, I think we have to stop the attacks."
Shays mustered 32 percent of the vote at the convention, assuring himself a spot on the primary ballot and earning the endorsement of conservative lightning rod Karl Rove, who did a Greenwich fundraiser for Shays last week.
Lumaj discounted Rove's appearance, saying it proves the status of Shays as a Washington insider.
"Seeing Karl Rove actually coming to the state of Connecticut and supporting Christopher Shays is actually a concern to me," Lumaj said.
Shays spokeswoman Amanda Bergen characterized Rove's seal of approval as something Republicans shouldn't take lightly.
"Karl Rove has one of the best strategic political minds in the country," Bergen said. "Rove has analyzed this race in terms of who will best help Republicans take control of the U.S. Senate in November and he believes Christopher Shays is the candidate in Connecticut who can help make that happen."
Lumaj served up a generous helping of red meat in his lone television ad during the campaign, proclaiming himself "unapologetically American and absolutely conservative."
"I want to continue the Reagan revolution," Lumaj said in the spot.
The married father of three fled the communist regime of his Balkan homeland 23 years ago and earned his U.S. citizenship five years later.
"I think that my campaign did capture the attention of the conservative base," Lumaj said.
Lumaj estimated that there are more than 11,000 Albanian-American voters in Connecticut, a demographic that Shays has tried to tap into.
Last Saturday in Waterbury, Shays attended the seventh annual Albanian Festival.
"He realizes that the Albanian-American community is very powerful," Lumaj said.