WASHINGTON — Scott Walker’s rivals see him as an up-and-comer in the Republican race for president, so they are focusing on the Wisconsin governor’s changing positions on a number of issues.

The still-unofficial campaigns of several Republicans have assembled internal memos, research papers and detailed spreadsheets that highlight and track Walker’s shifts on positions from immigration to ethanol to abortion.

They say Walker has a broad pattern of flip-flopping that will be his greatest vulnerability.

The rush of what’s known in the campaign trade as “opposition research” comes as Walker is in midst of a swing through two early voting states. He travels next week to South Carolina after spending this weekend in New Hampshire.

Steve Duprey, a Republican national committeeman from New Hampshire who is not aligned with any candidate, said Walker is relatively unknown among voters in his state — meaning the governor is subject to definition by his opponents.