Sen. Ben Sasse (R-NE) will absolutely not be an independent candidate for president in November, his team confirmed to Breitbart News on Monday morning. A high-placed source close to former Florida Gov. Jeb Bush has also confirmed that it will not be him running against presumptive GOP nominee Donald Trump and likely Democratic nominee Hillary Clinton in November. Another high-placed source, this one close to Sen. Ted Cruz (R-TX), has confirmed that the Texas senator—Trump’s last serious competitor for the GOP nomination—will also not be launching an independent bid for president in November.

Sasse, an outspoken critic of GOP presidential nominee Donald Trump from the beginning, has said he will not support Trump in the general election against Clinton.

Sasse is still holding out against Trump, drawing criticism from even his fellow Nebraskan Sen. Deb Fischer (R-NE)—who told the New York Times his strategy would hand Clinton the election.

“I don’t agree with his strategy,” Fischer said. “I’m not going to hand this election to Hillary Clinton.”

Bush and Trump, meanwhile, tangled roughly during the primary, and he has said he will not support Trump in the general election. Trump repeatedly called Bush “low energy,” and Bush made himself the tip of the spear against Trump for some time. Trump succeeded, while Bush failed, in the primary. Bush dropped out after a dismal performance in South Carolina, but he still refuses to back Trump against Clinton.

“In November, I will not vote for Donald Trump or Hillary Clinton, but I will support principled conservatives at the state and federal levels, just as I have done my entire life,” Bush wrote on Facebook back on May 6. “For Republicans, there is no greater priority than ensuring we keep control of both chambers of Congress. I look forward to working hard for great conservatives in the Senate and House in the coming months.”

The race between Trump and Cruz, meanwhile, was easily one of the most vicious in GOP history, where things got personal between the candidates and their families. But Cruz is definitely not running for president as an independent now, even though he has yet to formally endorse Trump after the bruising primary.

Sources close to several other potential high-profile independent candidates, such as 2012 GOP nominee Mitt Romney, have not yet confirmed one way or the other whether they are going to run. Several sources from Romney’s 2012 campaign are not exactly sure either way, though they believe Romney will end up not doing it. Some Republican officials are nervous it could be him who the Weekly Standard’s Bill Kristol has drafted as an independent, and the level of quiet from Romney-land at this time is concerning to some. Two of Romney’s current staffers have not answered repeated inquiries from Breitbart News as to whether he will go down this road, and he is about the only person with the name identification necessary to launch an effective independent bid for the presidency.

Republicans are fairly confident that 2008 GOP presidential nominee Sen. John McCain (R-AZ) will not run as an independent in November and similarly confident that U.S. House Speaker Paul Ryan—the 2012 GOP vice presidential candidate, Romney’s running mate—is not the candidate. Even so, McCain’s offices and Ryan’s offices have not responded to comment requests as of press time on Memorial Day.

If Kristol is unable to get one of those three—Romney, Ryan, or McCain—or another previous candidate for president like Wisconsin Gov. Scott Walker or Ohio Gov. John Kasich to run, his quixotic bid is unlikely to be even remotely successful. Walker’s team and Kasich’s team have not immediately responded to Breitbart News inquiries over Memorial Day weekend, but party insiders don’t expect either to launch an independent bid for president.

Every other former GOP presidential candidate from Sen. Marco Rubio (R-FL) on down to former Arkansas Gov. Mike Huckabee, former Pennsylvania Sen. Rick Santorum, former Louisiana Gov. Bobby Jindal, and all the rest of them have endorsed Trump–except for former New York Gov. George Pataki. If Pataki ran as an independent, though, it would be hard to take his candidacy seriously–he barely ever cracked a single percent in polling during the GOP primary.

For such an independent bid to be successful—success being defined as getting into debates and actually affecting the two major parties’ candidates, Trump and likely Clinton—any potential candidate would have to have enormous name identification already built up. They would also have to have vast resources, or access to major donors, since getting on the ballot across the country in enough states to matter as a candidate would be difficult and, without the backing of a serious party, such an independent could be even less successful than libertarian candidates.

It’s a possibility that Kristol does not actually have a serious candidate, or that he has a backbencher Congressman or former congressman or senator or former Governor lined up. Such possibilities for Kristol’s search for an independent to take votes away from Trump include, sources say, former U.S. Sen. Jim Talent from Missouri or former U.S. Sen. Tom Coburn from Oklahoma. Sources close to Talent and Coburn have not yet confirmed either way to Breitbart News whether they plan such a run.

[Update: A spokeswoman for Sen. Talent, after publication of this article, confirmed that he is not running for president as an independent and is not the candidate Kristol has talked about.]

Getting beyond that list, into House members and former elected officials, the roster is an endless possibility of no-name candidates that would not mean success for those seeking a seemingly desperate independent candidate for president.

[Update: Carly Fiorina’s team also confirmed she is not planning an independent bid for president.]