Jan 11 (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 to be spent on U.S. political advertising this year, the firm said. Broadcast TV remains favored in political advertising due to its ability to reach a broad audience.

Political ads are ramping up on the airwaves ahead of the Nov. 5 election. Supporters of Republican candidates Ron DeSantis and Nikki Haley aired attack ads targeting each other ahead of their head-to-head debate in Iowa on Wednesday.

Digital platforms will see the largest growth among various platforms for political ads, with revenue rising 156% from 2020 to $3.46 billion this year, the firm estimated.

Connected TV, in which viewers can watch YouTube or Hulu on their TV sets, is driving digital growth because it allows for more granular ad targeting and can cost less than broadcast TV ads, Newman said.

"It allows people with less funding to be able to reach the same screens," he said.

(Reporting by Sheila Dang in Austin, editing by Deepa Babington)