Yes, it can.
Just going along the mediterranean cost there is a nice chain of dialects from Roman, Tuscan, Ligurian, Provençal, Langedoc, Catalan, Southern Castillian to Portuguese. Maybe there is a break between Southern Castillian and Portuguese and you have to make a detour to the North of Spain via Madrid, Leon (Leonese), and Galicia (Galician) to have a real dialect continuum.
The issue with Southern Spain and Portugal is that the historic dialect continuum was disrupted by the Islamic invasion of Spain. During the reconquest, dialects from the north spread southward. There is still a considerable mutual intelligibility between Spanish (Castillian) and Portuguese, but I am not sure whether it is enough to count as a dialect continuum in Southern Spain. On the other hand, there is a dialect continuum between Portuguese Galician and Leonese closing the path through the north of Spain.