"To regain the lead" means to once again be in a position of advantage or ahead of others in a competition, race, or situation. It implies surpassing or overtaking your opponents or competitors after falling behind initially. Full definition
But after Iceland equalized, Portugal would not regain the lead in a Euro game until the final three minutes of extra time in a knockout stage win over Croatia. (caughtoffside.com)
The Senators regained the lead on a backhander by Cody Ceci with 5:26 remaining in the second. (si.com)
Recognising his tremendous efforts, he was promoted to be the general manger of China's Great Wall brand in August this year, in an effort to regain a leading position in the China market and improve its brand recognition. (thedrinksbusiness.com)