You can but if your unit ends in the attacked space your support is invalid. In your case it is impossible for Por to move out so Spa's support is invalid because it was attacking its own country. If however Por supported Mao into Spa and spa successfully moved out then the support would be valid.

Got it. Thanks.

There is one more case where the support does count. And that is to bounce against others. For example, you order MAO to support Por to Spain while you have a unit in Spain just sitting there. The other player orders Mar to support Gulf of Lyon to Spain. Por and Gulf of Lyon both have a strength of 2 so bounce and your unit in Spain just sits there. If Spain was supporting a hold or a move to anywhere but Gulf of Lyon it's support would be cut. But it is otherwise unaffected.

It's easy to remember, supporting an attack on your own unit can be done for defensive pruposes, but the support will NOT be taken into account for offensive purposes. You can support to force a bounce but never dislodge you own nation. For that matter, an ally can support your attack on your own nation and it will still result in a bouce if need be, but will not dislodge your unit. This is very useful when a front line unit needs to issue an attack (therefore support hold won't work) but you need to make certain an enemy on the front line doesn't move in behind you.

@Draugnar:

"For that matter, an ally can support your attack on your own nation and it will still result in a bouce if need be, but will not dislodge your unit."

That's not wrong, but is misleading. It can be read that any ally can't dislodge your unit.

The rule is very simple. Your support cannot dislodge your own unit. It can bounce your own unit, bounce someone else's unit, but if your support would cause your unit to dislodge, it won't happen. In the Por->Spa example, if GoL wasn't supported for some reason, Spa would be safe even though it was attacked with support, because the support came from you.

Here's an interesting question.

France:
Spa->Mar
Por->Spa

Italy:
Mar H

England:
F MAO S Por->SPa

Spain bounces, and Portugal is supported into Spain. I can't imagine that Spain is dislodged, but the support comes from another country. Anyone seen this happen?

Page 13 of the 2000AH Rulebook:

"A country cannot dislodge or support the dislodgement of one of it's own units, even if that dislodgement is unexpected"

See diagram 23 on that page.

Spa, Por and Mar all stay where they are.

This is a bounce all round, as your attacking unit cannot dislodge any of your own units.

@JBA

Um, ain't that what I said??? "For that matter, an ally can support YOUR attack on YOUR own nation and it will still result in a bouce if need be, but will not dislodge YOUR unit."

I enhanced the "YUOR"s for clarity, btu that is EXACTLY what I said. You can neither dislodge nor support a dislodgment of your own unit.

oops, "YOUR"s and "but"

As I said, it wasn't wrong, but can be read incorrectly. I just wanted to clarify.