Sen. Pat Toomey, R-Pennsylvania, announced his support for presidential candidate Marco Rubio on Wednesday. With endorsements from South Carolina Sen. Tim Scott on Monday and from two House members on Tuesday, Rubio will finally - finally! - overtake former Florida Gov. Jeb Bush for the lead in the count of endorsement "points" on the political website FiveThirtyEight.
Members of Congress aren't the only ones moving to his corner this week. The Florida senator also picked up supporters in Arkansas, Pennsylvania and Virginia.
We've seen this pattern before. In 2004, Democratic party actors mostly sat on their hands until Iowa. When then-Massachusetts Sen. John Kerry won there, the party rapidly rallied behind him, and he won the nomination easily. In 2008, Arizona Sen. John McCain had an early lead in Republican endorsements but they flattened out. When he showed new life in Iowa, finishing just a few votes from third place with 13 percent of the vote, the party rallied behind him, and he, too, went on to win.