By James Oliphant and Gram Slattery DES MOINES, Iowa (Reuters) – Donald Trump’s Republican rivals are scrambling for every vote they can get in Iowa, where the first Republican presidential nominating contest is now just days away. But when it comes to his actions involving the Jan. 6, 2021, attack on the U.S. Capitol, they are largely giving him a pass. They are not alone. At campaign events and town halls in Iowa, where voters will make their decision on Jan. 15, the attack rarely comes up. The candidates don’t mention it and neither do the voters, even as the country prepares to mark the th…