"Tomorrow you have the opportunity to vote for a Republican nominee for president," Romney said in the call. "I believe these are critical times that demand a serious, thoughtful commander in chief. If we Republicans were to choose Donald Trump as our nominee, I believe that the prospects for a safe and prosperous future would be greatly diminished - and I'm convinced Donald Trump would lose to Hillary Clinton. So please vote tomorrow for a candidate who can defeat Hillary Clinton and who can make us proud."
Although Trump has been largely immune to both self-inflicted damages and the flights of verbal arrows sent his way by Rubio and Cruz, old-school Republicans gathering in Park City, Utah this week continue to believe he's vulnerable.
The problem for the party is that no consensus has formed around an alternative. Cruz has the most the delegates, but he remains unpopular with many in Republican circles and among his colleagues in the Senate.
Though Rubio won recent contests in Puerto Rico and Minnesota, he's mostly been a distant third in other races, and Kasich, a distant fourth.
Privately many rank and file Republicans are hoping that "someone" simply garners enough delegates to mount a credible convention challenge.
To be sure, Trump's week thus far has not been all smooth sailing. After he asked attendees at a weekend rally in Orlando, Fla. to raise their rights hands and pledge to vote for him in next Tuesday's Florida primary, some likened the scene to Nazi rallies presided over by Adolph Hitler in the 1930s.
Appearing by telephone of ABC's "Good Morning, America" Tuesday morning, Trump said he hadn't heard such comments and rejected the Hitler comparison.
In a separate interview with MSNBC's "Morning Joe" Tuesday, Trump dismissed the charge as "ridiculous."
But then he came under fire for an entirely different reason and from what some might have thought an unexpected source the Better Business Bureau.
During a Republican candidate debate last week, Trump claimed that Better Business Bureau ratings for his controversial and now defunct Trump University had improved over time and that the school had ultimately earned an "A" rating.
Trump also said he had received a fax from the Better Business Bureau attesting to those statements.
But on Tuesday, the bureau said the school, the subject of a civil lawsuit, has no rating at all, and further, that it never sent a document of any kind to Trump prior to the Republican debate.
In a lengthy statement of its website, the bureau said, "The BBB Business Review for this company has continually been "'Rating' since September 2015. Prior to that, it fluctuated between D- and A+."
"The document posted on social media on Thursday night was not a current BBB Business Review of Trump University. It appeared to be part of a Business Review from 2014," it said.
On the Democratic side, Clinton's advantage in recent polls in Michigan and Mississippi suggested easy victories that would render Sanders's path to the Democratic nomination all but impossible. But the knockout blow didn't come and that's ratcheted up the import of next week's contests in Florida, Ohio and Illinois.
Tuesday's vote came against the backdrop of increasingly clarity in the race after former New York City Mayor Michael Bloomberg abandoned thoughts of launching an independent campaign for the White House.
Bloomberg, who served as mayor from 2002 through 2013, said in early February that was concerned about the negativity and extreme rhetoric that had defined the race for the White House, and confirmed he was considering spending as much as $1 billion on a presidential run.
On Monday, he posted an online editorial that poured cold water on those plans, saying that if he had run, it was unlikely any candidate would win a majority of electoral votes, which would then allow Congress to choose the next president.
"As the race stands now, with Republicans in charge of both Houses, there is a good chance that my candidacy could lead to the election of Donald Trump or Senator Ted Cruz. That is not a risk I can take in good conscience," Bloomberg said.
"I have known Mr. Trump casually for many years, and we have always been on friendly terms," he continued. "I even agreed to appear on 'The Apprentice' twice. But he has run the most divisive and demagogic presidential campaign I can remember, preying on people's prejudices and fears. Abraham Lincoln, the father of the Republican Party, appealed to our 'better angels.' Trump appeals to our worst impulses."
He said Cruz is almost as bad.
"Senator Cruz's pandering on immigration may lack Trump's rhetorical excess, but it is no less extreme. His refusal to oppose banning foreigners based on their religion may be less bombastic than Trump's position, but it is no less divisive," Bloomberg said.
"We cannot 'make America great again' by turning our backs on the values that made us the world's greatest nation in the first place. I love our country too much to play a role in electing a candidate who would weaken our unity and darken our future and so I will not enter the race for president of the United States," he added.
Trump and Bloomberg weren't the only ones making headlines early Tuesday morning. As voters in Mississippi and Michigan prepared to head to the polls, Marco Rubio's campaign accused Ted Cruz of spreading false rumors in Hawaii that the Florida senator had dropped out of the race.
Emails that appeared to have come from the Cruz campaign were sent to Rubio supporters in Hawaii with a link to a CNN report saying some of in the senator's camp saw no way for him to secure the Republican presidential nomination.
Joe Pounder, a spokesman for Rubio, said the claims in the email were entirely false.
"Senator Cruz is up to his dirty tricks again spreading false rumors and lies," Pounder said.
It also purportedly quoted Hawaiian caucus voters as saying they did not want to waste a vote on Rubio because he was likely to drop out.
The Cruz campaign ultimately disavowed the email, saying a volunteer had sent it out without permission.
Party officials in all four states told Courthouse News throughout the day Tuesday that voting in nearly all precincts was moderate to heavy.
"I'm expecting a good turnout with the enthusiasm we've seen over the past week or so, especially coming of the excitement of last weekend," said Paul Kanan, the spokesman for the Michigan Democratic Party.
On Saturday, Bernie Sanders took two Democratic primaries and was competitive in a third, giving a voters a sense that the race for the party's nomination is far from over and that their vote could make a difference.
"It doesn't hurt that the weather is absolutely perfect for voting, either," Kanan said.
In Hawaii, Andrew Walden, chairman of the Hawaii Republican Presidential Caucus Committee, said interest in the state's caucus was at something approaching an all-time high.
"The phones are ringing off the hook," he said.
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