Former presidential candidate Mitt Romney's upcoming speech denouncing Donald Trump's candidacy for the GOP presidential nomination is most likely coming too late, and could backfire by adding fuel to Trump's campaign as an anti-establishment candidate, panelists on MSNBC's "Morning Joe" program agreed Thursday morning,"He can't stop Donald Trump," Bloomberg Politics Managing Editor Mark Halperin, who released excerpts of Romney's speech Thursday morning, told the program. "The three candidates left in the race, [John] Kasich, [Ted] Cruz and [Marco] Rubio are the ones that have to do it."If Trump is to be stopped, he continued, it will have to happen in the next two weeks, particularly in Florida and Ohio, and "Mitt Romney wants to frame the argument."The former Massachusetts governor "does have a unique voice in the party," Halperin continued. "This speech, the parts of it I've seen, are very tough on Trump and on Hillary Clinton and I don't think people should overstate the impact it can have."But on the day of the debate leading up to tonight's debate, there will be discussion of the ideas Mitt Romney is putting forward about Donald Trump and Trump's reaction to it and that's part of what Gov. Romney, I think, wants to see."There are many people who would like to see Romney jump into the race, but that is not what the speech is about, said Halperin, who pointed out that Romney accepted Trump's endorsement for his own presidential candidate four years ago."He didn't make Donald Trump, but he was part of validating him as an important figure within the Republican Party four years ago," Halperin said."The governor is not sure which of the three candidates can stop him so today he'll praise Cruz, Rubio, and Kasich and say they're all good."Part of the problem is that "you can't get real now," show co-host Mika Brzezinski said."If you don't have something to offer, if you're not going to jump in and get the fight, then what is it that you're saying or doing at this point? Donald Trump is going to eat him up. Eat him alive. We've already seen this story and it hasn't happened yet. I know how it ends. "Former RNC Chairman Michael Steele commented that he does not know how establishment Republicans think Romney's speech will work, or who they think it is going to influence."Keep in mind, Mitt Romney lost 3 million Republicans who did not even bother to show up at the polls in 2012 to vote for him because they did not support his campaign," said Steele."To double back and go after the very guy who has brought them back into the party, you cannot lose sight of the fact that regardless of what you think about Donald Trump and feel about him, the establishment system is going to need this man, even if he's not the nominee."