The chances of former National Security Adviser John Bolton testifying in the Senate impeachment trial are seemingly increasing.

Sen. Mitt Romney (R-Utah) said Monday that, having spoken to other Republican lawmakers, it's "increasingly likely" more of them will vote to call Bolton to the witness stand now that revelations from his forthcoming book about Trump's alleged Ukraine quid pro quo were leaked to the public. Romney and Sen. Susan Collins (R-Maine) have maintained they'd like to hear from Bolton throughout the process. Collins reiterated that sentiment Monday, saying the Bolton leaks strengthen her stance on the matter and that she's working with Romney and Sens. Lamar Alexander (R-Tenn.) and Lisa Murkowski (R-Alaska) to bring in witnesses.

My statement on Bolton developments. pic.twitter.com/3M59J7suts — Sen. Susan Collins (@SenatorCollins) January 27, 2020

Those four have long been considered the best bets to go against the grain in the trial, but it now looks like other party members are willing to discuss the matter.

Don't expect everyone to jump ship, though. Axios reports that party leadership and the White House will continue to resist witnesses to prevent the "floodgates" from opening. One top aide told Axios that if Bolton's testimony were to implicate Trump, calls for acting White House Chief of Staff Mick Mulvaney and Secretary of State Mike Pompeo "will intensify." Read more at Axios. Tim O'Donnell