Final answer:
William Jennings Bryan, known for his 'Cross of Gold' speech and advocacy for the free silver movement, is the 'silver-tongued orator of the Platte'.
Step-by-step explanation:
The politician referred to as the "silver-tongued orator of the Platte" is William Jennings Bryan. He was a Nebraska congressman and a captivating public speaker who championed the cause of bimetallism and the free silver movement. Bryan became famous for his "Cross of Gold" speech during the 1896 Democratic National Convention, where he powerfully advocated against the gold standard and for the inclusion of silver to back the nation's currency. He was nominated as the presidential candidate by both the Democratic and Populist parties that year but was ultimately unsuccessful in his bid for the presidency.