It comes as very bad news for Republicans in general, and Ohio Republicans in particular, that Hillary Clinton’s odds of winning the Buckeye State this year are 66.4 percent to 33.5 percent for the Grand Old Party’s soon-to-be crowned presidential nominee, Donald John Trump.

The calculations behind how Ohio voters will likely act this fall come from Nate Silver, the reigning champion of political polling who correctly called every state in 2008 and all but one in 2012. FiveThirtyEight, Mr. Silver’s highly read blog on political calculus, takes a look at national and state polling so far this year.

In Ohio, the most important battleground state in the nation, the Donald is behind Clinton but not by much. Nate Silver takes the last 15 polls of Ohio voters and shows where the candidates stand. Gary Johnson, the former governor of New Mexico best known for his openness to legalizing marijuana both for medical and recreational uses, is a factor but not a big one. Mr. Johnson, who Libertarian Party backers are being directed to vote for, claimed eight percent in the last Quinnipiac Poll done June 8-19. The survey of 971 registered voters had Hillary Clinton at 38 percent with Donald Trump within the margin of error at 36 percent. Gary Johnson is more likely to siphon off votes from Trump more than Clinton.

Clinton’s numbers have gone up while Trump’s have gone down over recent weeks. Back in May-April, the Donald was ahead of Hillary by two percentage points. Candidates who win Ohio are most likely to be elected president. The last Republican candidate to win Ohio but lose the White House was Richard M. Nixon in 1960.

Nationally, Nate Silver tells us, Hillary Clinton’s chances of winning it all today is 78 percent compared to just 22 percent for Donald Trump. Both national political conventions will start soon, in one week for Republicans who will gather in Cleveland and Democrats a week later in Philadelphia.

Winning Ohio is big, for sure. It’s even bigger because the Buckeye State is ruled from top to bottom by Republicans. Ohio’s lame duck governor, John Kasich, is now a personal nongrata in Cleveland because he’s refused to lend even a crumb of support for Donald Trump. John Kasich appears, at this time at least, to have no official role or speaking spot in his party’s big meeting in his home state. What he will do for four days and four nights in Cleveland is still mostly a mystery, even though he’s said he’ll focus on electing down-ticket GOP candidates like Ohio’s junior senator in Washington, Rob Portman.

John Kasich was the last of 16 other candidates challenging Donald Trump to drop out of the race. Claiming he didn’t have the money to get his message of hopes and hugs across to voters, he lost 49 state primaries and won just one, Ohio. Even in his home state, he couldn’t capture 50 percent of primary voters, many of whom switched parties to vote for him in an effort to cause trouble for Trump.

Gov. Kasich has seen his mission from the Lord to be president go up in smoke, so if Mrs. Clinton does indeed become the 45th president of the United States, Mr. Kasich’s hopes and dreams of being the leader of the free world will likely disappear for good after she is sworn-in next January.

If Hillary Clinton wins Ohio by more than five percentage points, others in the know say that will help former Gov. Ted Strickland defeat Rob Portman who will have Mr. Kasich an every other Republican in Ohio working on his behalf.

Mr. Kasich may have a role after all, one he might not want, if unrest or riots break out as some worry about. “I’m nervous as hell,” Nina Turner, a former Democratic state senator from Cleveland who co-chairs the Ohio Collaborative Community-Police Advisory Board, told the AP. Turner said the convention “was going to be a powder keg all along.”

“This just puts more gasoline and dynamite and the match on top of all of that,” she said, referring to the fatal shoots of five police officers in Dallas over the weekend. If Cleveland turns into a powder keg, as Mrs. Turner suggested it might, Gov. Kasich can show what a uniter he is given his repeated claims on the campaign trail that he can unite people to come up with solutions to problems.