I am all-in on RG III: Rex Grossman III. Look it up: The Washington Redskins already have an RG III. And he will be entering his fourth year in Kyle Shanahan’s system, not his first.

All right, Rex isn’t the answer just as John Beck isn’t the answer behind center for the Redskins.

But it’s almost frightening to watch this instant infatuation Washington fans and media members have developed for Robert Griffin III, who looks tremendous in Spandex but has yet to put on pads and helmet for an NFL game.

But at least he’s in good company.

Last month, Green Bay free agent Matt Flynn was the homeroom crush. Last week, it was Peyton Manning.

We are turning into the dog from the movie “Up.” Someone blurts out, “Quarterback,” in this town, and we jump. Our tails vibrate for hours. We don’t know what we want; we’re more fickle than Michaele Salahi.

We’ve met the enemy, Washington; it’s us. We were supposed to keep Daniel Snyder sober from his shopping addiction, from throwing away draft picks and mortgaging the future on one player.

Remember the Shanaplan? Build. Build. Build. We were supposed to advocate for stability, the notion that slow and steady wins the race.

But as soon as the first shiny object runs by, we can’t help ourselves.

Pre-Shanahan and Bruce Allen, everybody skewered Snyder because he treated every player he wanted like a new bike in the toy-store window: I want that one.

Yet that’s exactly what we’re doing with RG III.

I respect Jason Reid and Sally Jenkins boatloads (customary Post disclaimer before torching our colleagues), but what are they thinking?

Sal last month on acquiring a fused-together Manning, who will probably play with a G.I. Joe swivel arm in September: “Do it.” JR I on RG III, whom he suddenly has a bro-mance with: “Do it. At any cost.”

I thought they were actually hyping movies. You know, where the ad guy takes the two kind words out of a critic’s blistering review — “Muppets on Ice:” Electric! Opulent! — to push sagging ticket sales.

Look, Robert Griffin III is a special quarterback capable of having a successful NFL career of 10 years or more. And, of course, there’s no discounting that the potential of an African-American star in this city makes Griffin even more appealing.

But no one knows for certain if he will be a Pro Bowler, if he can dissect NFL defenses the way he dissected an Alamo Bowl opponent.

I hate to break this to everyone, but someone wins the Heisman Trophy every year, and often it’s a quarterback. In fact, Gino Torretta has a trophy, too. Next season, Matt Barkley or Landry Jones will probably vie for the award that goes to college football’s best player.

Why not build up the offensive line, the receiving corps or find a shutdown corner and then go all-in for Barkley next year? He was thought to be a higher pick than RG III, after all, before he decided to return to Southern California.

All we apparently know about RG III in the NFL is that the St. Louis Rams are not interested in drafting him at No. 2. Trading Sam Bradford to make Griffin their starter is not in their thinking. That means Jeff Fisher believes Bradford, who is not as nimble in the pocket and certainly not the dual threat Griffin is as a scrambler, has a better NFL future ahead of him.

Think about that: Bradford gave the Rams hope with seven victories his first year, but he was banged-up and injured for much of his second season. No one has inducted him into the Brady-Rodgers-Brees-Eli-Big Ben pantheon of best NFL quarterbacks right now. And Fisher still believes Bradford will make the Rams better in five years than Griffin would.

Further, Mike Shanahan is oh-fer in the QB-selection game thus far in Washington. He’s at least 0 for 1 in the Face of the Franchise selection game, too.

Do you know the last “It Guy” in Ashburn, a player whose telegenic smile and talent sold club-seat contracts to gullible burgundy-and-gold legions whose current club-seat deals had expired after 10 years? Donovan McNabb.

How’d that work out, kids?

But, but RG III is young and impressionable. He has so much upside. He might even do what Kyle tells him.

This is the scariest part of the logic behind going all-in for RG III: It perpetuates the falsehood that this franchise is one player away, albeit one at the most important position.

This isn’t the NBA; you don’t trade for Shaquille O’Neal in Miami one offseason and win a title two years later. The Redskins have needs at multiple positions.

So it comes down to this: Do you trust the personnel acumen of Shanahan more than Fisher?

I will start trusting Shanahan if he genuinely sticks to the plan. Again, build, build and build. Offensive line. Receiving corps. Defensive backfield. When all the areas are addressed to allow a quarterback to stay upright and productive, progress will truly be made.

It just seems ludicrous that the only answer is suddenly to go get this pick, irrespective of the fact that the Cleveland Browns have more to offer with two first-round picks this season — including the No. 4 overall, two slots higher than the Redskins’ top spot. If the Rams use the Browns as leverage, all of a sudden the asking price is upped considerably and fair-market value goes out the window.

Besides, a major part of RG III’s game is tucking the ball and running. Running quarterbacks in the NFL wind up in two places: the ground and the injury list. But don’t let the facts get in the way of the visceral reaction to give up the store to ensure he plays in Washington, because we have become very good at substituting hope for reality.

Crazy, no? Many of the same people eviscerating this team for being so irresponsible over the years have decided responsibility is suddenly boring and want to go for it.

We’re all-in again for one player who we are absolutely certain can be the answer to all the franchise’s problems. Throw away picks. Spend, spend and spend more.

Weren’t we, Allen and Shanahan supposed to keep the owner in check, help with recovery and curtail his addiction? So why does it feel like Daniel Snyder’s support-group sponsor just turned into Charlie Sheen, gassing up a Vegas-bound Porsche.


We’re still so sadly predictable.