Radak: It is "Malkeinu"; the matter is repeated in different words. Our king, i.e. David, Shlomo and those who came after him from his seed, are to Hashem (fear him; this is like "Mi la'Shem Elai" (Shemos 32:26). Therefore, he succeeds and overpowers his enemies.

Malbim: This corresponds to Hashgachah via nature. Corresponding to Hashgachah via wonders, it says "v'Likdosh Yisrael Malkenu." When Hashem's name is mentioned Stam (without Yisrael), it hints that He is the Creator who sustains the world's existence via general conduct. When His name is mentioned with Yisrael, e.g. Elokei Yisrael, Avir Yisrael, Kedosh Yisrael, it refers to the wonders that He does for Yisrael and His clinging to them. Kedosh Yisrael intends for His connection to Yisrael via the Kedushah of their deeds; Malkenu adds that we are elevated via wonders that He does via Malchus Beis David. Via nature, He is a shield to us - this is attributed to being the Creator and Conductor.