Irishman Cronin holds a 3.3sec advantage over Northern Ireland’s Alastair Fisher (pictured). Sebastien Chardonnet lies third, 6.6sec behind Cronin, all three drivers at the wheel of Citroen DS3 R3Ts.
Fisher won the opening stage, but Cronin was fastest on the next. Chardonnet claimed the third stage but Cronin was again quicker than Fisher to reduce the margin between the two to 11.3sec.
Cronin won the final all-gravel stage and moved to the head of the pack when Fisher damaged his suspension shortly before the finish and lost 15sec.
It promoted Cronin into a 3.2sec lead, but Fisher repaired the suspension on the following road section and the pair continued their battle on the final test in Lisbon, where the two were separated by just one-tenth of a second.
Christian Riedmann held third until he was sidelined at the end of SS3 with a technical problem. The only other retirement in the nine-car field was Frederico Della Casa who crashed in the opening stage.
The only other driver in touch with the top three is Bryan Bouffier, who lies 23.1sec behind Chardonnet.
Simone Campedelli was second quickest in the opening stage but dropped 3min 31sec in the next test. The Italian was quickest in the final test in Lisbon and lies sixth.