The always bilious and sometimes vulgar Donald Trump presidential campaign now turns toward primaries in Arizona and Utah having rolled over Marco Rubio in his home state, Florida.

Rubio, the junior Florida senator, quit the presidential race after Tuesday's humiliating result. But before heading for the exit, he warned his party that it was risking disaster for itself and for America.

"The politics of resentment against other people will not just leave us a fractured party; they're going to leave us a fractured nation," said Rubio. "They're going to leave us as a nation where people literally hate each other."

What a thing for a sitting senator to say about the direction of his own party — that it is encouraging the hatred of its people for each other — yet it didn't sound like mere sour grapes, it sounded genuinely fearful.

Whether the fracturing of the nation is truly nigh, the fracturing of the party is fully underway.

Notwithstanding Trump's calls for the party to unite behind him, it's become a time for taking sides in the Republican civil war.

Since former Republican nominee Mitt Romney said earlier this month that America's parents would be appalled to see their children behave like Trump, other Republican leaders have trotted out their anxieties too.

A Google search of "Chris Christie's humiliation" brings up 502,000 results along with images of Christie and Trump together. (Aaron P. Bernstein/Reuters)

Senate Majority Leader Mitch McConnell, House Speaker Paul Ryan and normally-easy-going Ohio Governor John Kasich, among others, have felt it necessary to call for Trump to say things that should normally go without saying — to condemn violence, racism and the Ku Klux Klan, for example — and caution that he not "prey on the fears of people who love our great country."

It seems too late in the game to expect stern warnings to make a useful difference, but possibly Republicans who are aghast at what they fear is befalling their party only want to be on the record as having warned of the catastrophe before it happened.

Or maybe, to them, the alternative just seems so unappealing.

There is the example of New Jersey Governor Chris Christie, who took a different path and opted to get behind Trump. In his new role as a Trump sidekick he is also the butt of Trump's jokes and it all turns out to be not as much fun as you might think.

"No, I'm not being held hostage," Christie told a reporter who apparently thought that was a reasonable thing to ask after seeing Christie on stage recently staring blankly into the middle distance from behind Trump's shoulder.

A Google search of "Chris Christie's humiliation" brings up 502,000 results along with images of Christie and Trump together.

Still, maybe it will all work out for Christie in the end. Maybe he's backed the right horse and will end up as an important sidekick in a Trump administration. Republicans have that to consider, too. After all, Trump's odds of winning the nomination are good — and they've improved after every important primary.

Even losing Ohio on Tuesday was not a bad thing for Trump.

Ohio Governor John Kasich won the primary, his first, only to face the "dog catches car, now what?" question. He will stay in the race, splitting the anti-Trump vote, but with no real prospect of winning the nomination because he has even fewer delegates than Rubio had — and Rubio dropped out because he didn't have enough.

The establishment effort to stop Trump really now rests solely on preventing him from winning a majority of delegates (1,237) before the party convention in Cleveland in July. If that happens, another candidate might win on a second or third ballot, so goes the theory.

But even talking about all that is dividing the party. Trump supporters argue he doesn't need a majority of delegates to become the nominee, he needs only to be "first past the post" — to have more delegates than any other candidate.

Trump's opponents say the process is designed so that the nominee is the choice of the majority of the party not just a plurality.

'Down ticket' impact

Before the convention in Cleveland there will be other Trump issues to divide people.

There's the "down ticket" impact of a Trump candidacy to work its way through the party as it gets ready for the general election.

A supporter shows off his very permanent tattoo before a Trump campaign rally in Ohio on Monday. (Aaron P. Bernstein/Reuters)

Twenty-four Republican senators and all house members are up for election in November — and they'll be on a ticket that will have Trump's name at the top if he becomes the nominee.

In some states and in some districts getting behind Trump might be an advantage, elsewhere it might be politically fatal.

So it's not hard to imagine how supporting or opposing Trump could become a litmus test in district primaries over the next few months. And it's not hard to imagine how easily those contests could turn ugly.

Over on the Democratic side, the race seems finally to be sorting itself out. Hillary Clinton not only won more delegates than Bernie Sanders did on Tuesday night, she won in the kind of "rust belt" states where there had been doubts about her "electability" after she lost a close race to Sanders in Michigan last week.