Gov. Tim Walz of Minnesota will speak at the state political conventions for Democrats in South Carolina and California at the end of this month, his latest effort to place himself in front of voters likely to be central to his party’s 2028 presidential nominating contest.

Mr. Walz, who was his party’s nominee for vice president last year, will deliver speeches at the two state conventions on the same day — May 31 — which his aides portrayed as a feat of political stamina and private air travel between Columbia, S.C., and Anaheim, Calif.

Since March, Mr. Walz has traveled throughout states President Trump won last year to hold town halls and address largely Democratic crowds in Republican congressional districts. Governor Walz spoke to the Democratic convention in Montana, where his daughter lives, and is also scheduled to speak to South Dakota Democrats in July.