“V” (8 p.m., ABC): In the gripping sci-fi remake “V,” aliens drop in on

“V” (8 p.m., ABC): In the gripping sci-fi remake “V,” aliens drop in on Earth, preaching peace and harmony. But is it a ruse? Elizabeth Mitchell (“Lost”) plays a suspicious FBI agent.

“By the People: The Election of Barack Obama” (9 p.m., HBO): This absorbing documentary is an up-close-and-personal look at Obama’s historic two-year journey to the White House. Filmmakers Amy Rice and Alicia Sams had unmatched access to the campaign as it moved through the arduous primary battles, the Democratic National Convention and Election Day. The result is a fascinating, behind-the-scenes look at political strategy-making, as well as candid moments with Michelle Obama and the couple’s daughters, Malia and Sasha.