By Sheila Dang (Reuters) – Spending on political advertising in the U.S. is expected to jump 30% this year from the last presidential election in 2020, partly driven by higher spending on digital platforms, research firm Insider Intelligence estimated on Thursday. Political candidates have larger advertising budgets, as polarized voters donate more to their picks and fundraising platforms make it easier to donate to multiple campaigns, said Peter Newman, forecasting director at Insider Intelligence. Traditional television ads will continue to make up the majority of the estimated $12.3 billion…