blonde poker forum

I know the rule, but why is it this way?

There's a raise,and  a shortstack moves all in and it's an 'under raise'

I know the original raiser can't do anything but call (or fold), but why is this?

Because no one has reraised him.

The under-raise is classed as a call.

The reasoning behind the rule I think is that to allow the underaise to re-open the betting would be to give excessive strength to the small stack.  Effectively anyone acting after the small stack would have to look at the stack size of the original raiser and not just the short stack.

In no limit, the original raiser has already had the option of betting what they want, and no-one has challenged that bet by re-opening the betting with a full raise.

ahhh (http://s3images.coroflot.com/user_files/individual_files/345330_p87t6rbh4umOULUIusn19L77x.jpg)

obvious when it's explained

The under-raise rule also applies in pot limit, so don't see that the amount of the initial raise is relevant.

NL and I believe PL too use the "full bet" rule. Fixed limit generally uses the "half bet" rule. e.g you open for 1000, short stack goes all in for 1500. In NL/PL you can only call. In FL you can raise.

I know that - I am challenging the assertion that the under-raise rule is in place because  the original raiser has already had the option of betting what they want

Lol, I only used no limit as an example, as it is easier to understand. Of course it is the same with pot limit, just trying to simplify.

The point is that if anyone checks/bets/raises they have "had the option of betting what they want" no matter what happens after them.  So using your logic no one should ever be able to do anything other than call after they have acted, because they have already bet "what they want".

In your first post all you have done is find a flowery way to restate the under-raise rule and not offer any explanation as to why in the unique situation of the under-raise the rule-writers considered making an exception to normal rules.

It's not an exception to the rules, it is the rule. It's like asking why do they make an exception for the flop and put three cards out there when the other streets only have one card each. The term raise has a specific definition that an underraise doesn't fulfil.

I give up

Firstly, let's say you bet 1,000 and everyone calls. You don't get the chance to raise because the betting is finished. You only have an option if you have yet to react to a change in action.

Now let's consider raising. The amount of a raise needs to be at least the size of a previous raise. This rule prevents "pointless" raises. e.g. you bet 1,000. I cannot raise to 1,025. We could be there all day.

But then we have the situation of the bet being 1,000 and someone only having 1,025 chips. In NL (and others to an extent, but stick with NL for simplicity) you are always allowed to wager your entire stack. So we allow the player to go all in for 1,025, but this is not a raise as by definition a raise must be the size of a previous raise. It is essentially a call.

Action now comes to the original raiser. Because we treat the all in as a call the action has not changed, therefore the original raiser does not have the option of raising open to him. But obviously in this special case you must call the extra 25.

The alternative of course would be to disallow the all in under-raise, but this is silly for a multitude of reasons.

So to put it in terms of your point.. when you are facing "new" action you have the ability to bet what you want. You only get this power when the action changes to you. In the instance of the all in under-raise then the action has not changed therefore you don't have that power.