For a while, it looked like Greg Kinnear showed his acting chops best with supporting roles in the likes of As Good as It Gets, Little Miss Sunshine and the current Ghost Town. Well, hang on. Kinnear takes the star spot in Flash of Genius and rides it to glory. He plays Robert Kearns, the Detroit professor, inventor and father of six who came up with the idea for the intermittent windshield wiper during the 1960s. Go ahead, groan. I felt the same way. A night reading patent law seems more exciting. But Kinnear takes this true story — John Seabrook’s 1993 New Yorker article formed the basis of the script, by Philip Railsback — and runs with it. Kearns had his “flash of genius” when a champagne cork popped his eye on his honeymoon with wife Phyllis (Lauren Graham). Why couldn’t a windshield wiper work like his blinking eye? Kearns got help from his friend Gil Previck (an excellent Dermot Mulroney) to build a prototype, get a patent and take it to the Ford Motor Company. Years later, Ford claimed the invention as its own — no credit or money to Kearns. Years of lawsuits ensued. One attorney, Gregory Lawson (a terrific Alan Alda), advised Kearns to settle. But Kearns wanted what Ford was unwilling to give: credit for the invention. The gauntlet was tossed. Kearns would represent himself in court, spending years in research, to the exclusion of his children and the wife who left him, to restore his good name in court. It’s a David-and-Goliath tale that recalls Frank Capra’s Mr. Smith Goes to Washington and Francis Coppola’s Tucker: The Man and His Dream. A fresh take would have helped. But Marc Abraham, in his directing debut, proceeds with a timid TV approach. Luckily, Kinnear ignores the “caution” signs. Kearns wasn’t a movie hero. His halting courtroom delivery lacked Hollywood histrionics. Kinnear plays him with blunt honesty, sagging under the weight of stress but maintaining a bulldog tenacity that would win the day. Was the battle worth it? Kearns’ conflict is readable in Kinnear’s every word and gesture. His performance is worth cheering.