Raj, who had joined BJP just a few months before the elections, polled 6,29,860 votes against Birla's 5,23,058.
Rakhi is MLA from Mongolpuri.
Union Minister and Congress' sitting MP Krishna Tirath polled 1,57,468 votes while BSP's Basant Panwar got 21,485 votes.
In the Delhi assembly polls in December, BJP had won five assembly seats that come under the constituency, followed by two each by AAP and Congress and one by an Independent.