A political adviser to Mr. Bloomberg said the billionaire former mayor of New York City would use his super PAC, Independence USA, to air intensive ad campaigns in all television markets in both states. The cost of the two-state campaign is expected to total around $15 million.

The decision by Mr. Bloomberg reflects just how much the electoral landscape appears to have shifted in the final few months of the presidential race, as Mr. Trump’s mismanagement of the coronavirus pandemic has intensified his unpopularity and further alienated crucial voting groups like women and suburbanites…

The Bloomberg team conducted polling in a number of states over the weekend and came away convinced that Texas and Ohio represented its best targets — narrowly divided electoral prizes where the war for television airtime is not already cluttered with heavy advertising on either side. The team presented Mr. Bloomberg with the numbers on Monday morning and he gave the go-ahead.