YOU KNOW what today is, right?

ASPCA Help a Horse Day.

And Pennsylvania Primary Day. (Also Delaware, Maryland, Connecticut and Rhode Island, but we are the Big Enchilada.)

This year, for a change, despite our late-to-the-party primary, Pennsylvania can be the La Brea tar pit for Bernie Sanders, Ted Cruz, and John Kasich. The dance can end here.

After the drubbing Sanders and Cruz took in the Vampire State - oops, Empire State - a Keystone State loss will be an insurmountable roadblock for the senators, who are playing hardball, and for the governor, who is playing Yahtzee. (The just-announced Cruz-Kasich Axis doesn't affect Pennsylvania.)

On the Dem side, front-runner Hillary Clinton has the major Pennsylvania political "names" in her handbag: Sen. Bob Casey, Gov. Wolf, and ex-Mayor and Gov. Ed Rendell. Neither Clinton has ever lost a statewide Pennsylvania election. History is destiny.

For Pennsylvania political endorsements, Sanders has (drum roll) Braddock Mayor John Fetterman, a/k/a Lurch, a candidate for U.S. Senate who is polling worse than the Zika mosquito. Also, the long-retired former mayor and congressman, Bill Green.

"This election will set a course for the next 50 years," says Laurance Rassin of the newly launched bipartisan, Philly-based Political Storm news site.

Although he thinks Sanders is the "ideal candidate" for Democrats, the Vermonter is tackling "the most powerful Democratic dynasty since the Kennedys," and, yes, the system is rigged against him.

Representing the Establishment, Hillary rides into Pennsylvania on a double-digit lead. A second big-state loss will separate Bernie from any logical reason to carry on, but he says he will.

A Clinton win should help Establishment-endorsed down-ballot candidates, but don't bet on it. Hillary has not endorsed anyone for U.S. Senate or attorney general.

In the Dem slugfest for U.S. Senate, Katie McGinty has President Obama's blessing, Joe Sestak boasts that the Establishment hates him, Fetterman is Sanders' copilot, while Joseph Vodvarka, the blue-collar Donald Trump, urges you to vote for anyone but Sestak. There are a very high number of "undecideds" in this race.

For attorney general, Josh Shapiro has the endorsement of Obama, Casey, and Wolf. Stephen Zappala and John Morganelli have no statewide Big Names. It is notable that Obama has injected himself into these state races.

If Hillary's pantsuit has coattails, they should benefit McGinty and Shapiro. But that is a big "if."

Trump's coattails could be a negative for GOP incumbent Sen. Pat Toomey, says Widener University's Wes Leckrone: "Toomey is already polling poorly and much of what he stands for as a free-market, pro-growth, limited-government candidate directly opposes the talking points of Trump."

In addition to figuring out what Trump is saying, the big fun is on the Republican side, if by "fun" we mean confusion and duplicity.

GOP voters will select 17 delegates pledged to the candidate who wins statewide, but 54 others will be uncommitted.

Who knew that? You learn so much when things go sideways, as in this crazy election.

Such as, what is the point of having delegates who are not pledged to candidates?

A big point - and a good one for Pennsylvania Republicans. Those unpledged votes might be the very ones Trump needs to make the magic number of 1,237 - or to stop him.

"Potentially, Pennsylvania's delegates have the capability of keeping Trump from securing the majority on the first ballot," says Sarah Niebler, a Dickinson College political science assistant professor.

That's a lot of responsibility in a few hands, and that translates to power. Reflecting on today's ASPCA horse theme, those votes are a stallion Trump wants to corral.

The best and most noble of the unpledged delegates will seek promissory notes to benefit the commonwealth. The other 96 percent will want to be Secretary of Something or Ambassador to Somewhere. If that sounds ridiculous, remember that Trump thinks he is the master of the Art of the Deal.

There's one thing wrong with the bargain. It will pay off only if he is elected president, and we know that just won't happen.

Don't we?

215-854-5977 @StuBykofsky

Blog: ph.ly/Byko

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