plus the half-time show that has everybody talking. this is the cbs evening news with norah o donnell reporting from the nation s capital. o donnell: good evening, and thank you so much for joining us. as we come on the air tonight, it s democracy in action. caucus-goers are beginning to gather at nearly 1,700 school gyms and community centers all over iowa. by the end of the night, we should know which candidate or candidates have scored the first points in the race for the democratic presidential nomination. 41 delegates are up for grabs. now that s just 1% of all pledged delegates that will be awarded during the democratic primary process, but iowa is all about seizing momentum. the top seven candidates have spent a combined 400 days campaigning in the hawkeye state. our cbs news battleground tracker has joe biden and bernie sanders neck and neck, but with very different bases of support. pete buttigieg and elizabeth warren are also still in the hunt. our team is cover