Wisconsin governor Scott Walker is endorsing Ted Cruz in the Republican presidential race.
Mr Walker announced his decision on Milwaukee conservative talk radio, saying: "It's time we elect a strong new leader. I've chosen to endorse Ted Cruz."
Mr Walker had signalled last week that he was likely to back Mr Cruz, saying then that he was the only candidate who has a chance at beating front runner Donald Trump. When Mr Walker ended his presidential campaign last year, he called on others to join him in dropping out to make it easier to defeat Mr Trump.
It is unclear how much Mr Walker's backing will help Mr Cruz in the state ahead of its April 5 primary. Mr Walker's approval rating has not exceeded 40% in over a year.
Mr Cruz said Mr Walker's "heroic" battle with unions inspired him and millions of others.
He called Mr Walker a "strong, principled conservative" and noted that he won three elections over four years. Mr Walker defeated a recall election in 2012 spurred by his push to all-but-eliminate collective bargaining for public workers.
Mr Cruz said "millions of men and women all across the state of Wisconsin stood with governor Scott Walker" during that fight.
He described it as a "heroic stand" that inspired millions across the country, including him.
Mr Walker says he plans to campaign with Mr Cruz this week.
Meanwhile, South Carolina senator Lindsey Graham has described Mr Trump's foreign policy as "gibberish" and "ill-conceived" and said he would be "worse than Obama" as president.
The Republican is leading a congressional delegation to Israel. Mr Graham, who dropped his own bid for the White House last year, told The Associated Press that Mr Trump does not understand the stakes of the Middle East. He took particular aim at Mr Trump's assertion that he would take a more neutral stand regarding the Israeli-Palestinian conflict.
Mr Graham said "this is not a real estate deal. This is the survival of the one and only Jewish state".
Mr Graham said he is concerned a Hillary Clinton presidency would amount to a third term for Barack Obama, but she was at least a "known quantity".
Mr Trump plans to make his first campaign appearance in Wisconsin with a rally in House of Representatives speaker Paul Ryan's home town.
Ohio governor John Kasich is keeping up his role trying to play spoiler for Mr Trump by campaigning in Wisconsin.
Ms Clinton is scheduled to participate in a gun violence forum in Milwaukee, while her rival, Bernie Sanders, is heading to Appleton and Milwaukee.