Do any scholars identify Tarshish with Tartessos, before the Malbim?
Among the classic Jewish works I've seen, Tarshish is nearly unanimously identified with modern-day Tunisia (Ibn Ezra, Targum Yonasan1, Rashi1); the two early dissenters I've seen quoted are modern-day Turkey (in the name of Antiquities) and modern-day Italy (in the name of the Abarbanel2).
אבל האמת עד כמ"ש בפי' ישעיה (סי' כ"ג) שתרשיש היא עיר טארזיס שהיא שפאניען הקדומה שהיתה רוכלת הצוריים בספרד, כמו שכתבו חכמי העמים, ונודע כי הצוריים בבואם לספרד, (אשר כינו בשם אושפניא ע"ש שהשפנים נמצאו שם לרוב) מצאו כסף מזוקק על פני הארץ הרבה מאד עד שעשו כל כליהם וגם חשוקי וווי ספינותיהם מכסף, ובנו להם עיר מושב ורוכלת העמים טערזוס, והעיר הזאת יושבת על מבואת ים האטלאנטי שהוא ים אקיאנוס, וידוע שיש סוף נכנס לים אקינוס, ולפ"ז באניות שבנה בעציון גבר היה יכול לילך בין לאופיר בין לתרשיש.
But the truth is as I wrote in my commentary on Isaiah 23, that Tarshish is the city of Tarzis, i.e. early Spain. For the Tyrians were merchants in Spain, as the wise among the nations have written, and it is known that when the Tyrians came to Spain (which they called Ushpania after the lagomorphs (shefanim) which were found in abundance there) they found silver scattered all over the land in abundance, to the point that they made all of their vessels and even the masts on their ships from silver. They built for themselves a city for dwelling and for merchants of the nations, Tarzis. This city sat on the Atlantic coast; it is known that a strait enters into the Atlantic Ocean [NB: the Strait of Gibraltar which connects the Atlantic and the Mediterranean], and according to this, with the ships build in Ezion-Geber [NB: near modern-day Eilat] he would have been able to travel to both Ophir and Tarshish.
The Malbim's description of Tarzis matches up with the legendary city of Tartessos. While it is unclear how much we know of the ancient city is mythical and how much is factual, we do know that it sat on the mouth of the Guadalquivir River, just west of the Strait of Gibraltar, that they were a shipping society which interacted heavily with the Phoenicians (in the time of I Kings on which the Malbim comments, that'd be the Tyrians), and that the region was rich in metal (particularly tin; the word כסף, which I translated above as "silver," often refers to metals in general).
While I do not know of a source that explicitly connects Tartessos to rabbits, it is known that several subspecies of lagomorph are native to the southern Iberian peninsula (ex. the Iberian rabbit, O. c. algirus and a subspecies of the Granada hare, specifically L. g. granatensis). Even the legend the Malbim cites regarding the etymology of the name Spain, while unverified, is not without precedent; he's not the only one who connects "Spain" and "Shafan."
For such a solidly-rooted position on connecting Tarshish and Tartessos, it's surprising to me that it took until the nineteenth century for a Jewish Biblical commentator to propose the theory. Following the Malbim, Jastrow identifies Tarshish with Tartessos, and Jewish Encyclopedia cites several secular scholars (but oddly enough not the Malbim or Jastrow) concurring with this identification.
With all of that said: Do any Jewish Biblical or Talmudic commentators identify Tarshish with southern Iberia who lived before the Malbim?
This link cites Targum Yonasan among those who refer to Tarsus, alongside Josephus. He seems to refer to pseudo-Jonathan on Genesis 10:4. This is not a Talmudic-era source, in spite of the author's claims; even if it were the same Targum Yonasan, there is nothing to suggest that טרסס is specifically Tarsus, Cilicia, as it could simply be the Aramaic spelling/translation of the word תרשיש; and if both pseudo-Jonathan is Targum Yonasan and טרסס being Tarsus are true, he contradicts himself from my link above where he explicitly refers to Tunisia. ↩
My translation ↩