Hi, this comes up from time to time and is well worth discussing because it can have a major impact on how a hand plays out.
Hand 1120038036
@Gezaclanismo raises to 750 and the big blind shoves for an additional 415. Replay (and many Rule setters) says that the under-raise is treated as a call which does not reopen the betting, therefore Gezaclanismo is not given the option to raise again.
Here is an example of a site which publishes Robert’s Rules of poker, which are widely accepted as a solid reference for all levels. (Credit to Bob Ciaffone).
Jump to SECTION 14
3. All raises must be equal to or greater than the size of the previous bet or raise on that betting round, except for an all-in wager. Example: Player A bets 100 and player B raises to 200. Player C wishing to raise must raise at least 100 more, making the total bet at least 300. A player who has already acted and is not facing a fullsize wager may not subsequently raise an all-in bet that is less than the minimum bet or less than the full size of the last bet or raise. (The half-the-size rule for reopening the betting is for limit poker only.)
4. Multiple all-in wagers, each of an amount too small to qualify as a raise, still act as a raise and reopen the betting if the resulting wager size to a player qualifies as a raise. Example: Player A bets $100 and Player B raises $100 more, making the total bet $200. If Player C goes all in for less than $300 total (not a full $100 raise), and Player A calls, then Player B has no option to raise again, because he wasn’t fully raised. (Player A could have raised, because Player B raised.)
Accordingly, in 1120038036, once the big blind has made their under raise, any player who limped for 200 should be able to raise (they have the option to reply to the raise of 550), but any player who has already called 750 has had their option to raise and may only call, including the initial raiser. - Even if they have another less-than-the-raise amount.
This may seem counter-intuitive, but the idea that in NL poker there are unlimited raises or you may go all-in any time is not 100% accurate. The rule basically protects players from calling a regular bet of whatever the pot is, then a relatively small all-in raise of a handful of chips to find themselves potentially exposed to a massive shove from the initial raiser.
In short The under raise does not reopen the betting.
The way to avoid being caught out here as the raiser with A A would be to either raise to a small amount which enables the big blind to make a full raise, or make a raise which covers the big blind’s stack.
Rob