As I have written frequently, the threat to defund Obamacare is both silly and irresponsible. Moreover, we have pointed out that the lion’s share of the funding comes from entitlement spending that will not be at issue when the fiscal year runs out.

Sen. Marco Rubio (R-Fla.) (Joe Raedle/Getty Images Sen. Marco Rubio (R-Fla.) (Joe Raedle/Getty Images)

Nevertheless, shortly after Sen. Mike Lee (R-Utah) proposed it, Sen. Marco Rubio (R-Fla.) joined in the gambit, to be followed by Sens. Ted Cruz (R-Fla.) and Rand Paul (R-Ky.) The shutdown contingent claims 12 GOP senators, leaving 88 who aren’t ready to participate in this scheme. Here are 10 reasons this is a mistake for Rubio.

1. You can’t out-crazy the crazies. Rubio won’t convince far-right-wingers he is one of them by indulging in this stunt.

2. It makes him look defensive about his immigration reform effort. Why else try to bend over backwards for the chance to ingratiate himself with the base?

3. He is smart enough to know that this gambit won’t work.

4. If he tries to be all things to all people he’ll wind up without a firm base of support.

5. It projects a lack of maturity and gravitas, both of which he will need to establish to clear the bar in a presidential race.

6. It takes time away from and diminishes his credibility on other topics like education reform.

7. It only highlights that inconvenient fact that he hasn’t presented a defined alternative to Obamacare.

8. His home-state press has figured out that the plan is “going up in smoke in the nation’s capital” and has triggered a “growing backlash” among Republicans.

9. He is not being honest when he says somehow this would be Obama’s fault (“the President will have a decision to make: sign it and keep the government open, or veto it and shut down the government”).

10. It will annoy donors and has already sewn dissension; party leaders have to reassure donors and unite the party.